Re: How many partition can one single machine handle in Kafka?
Todd, Thank you very much for your reply. My understanding of RAID 10 is wrong. I understand that one can not get absolute sequential disk access even on one single disk, the reason I'm interested with this question is that the design document of Kafka emphasize that Kafka make advantage of the sequential disk acceess to improve the disk performance, and I can' t understand how to achive this with thounds of open files. I thought that compare to one or fewer files, thounds of open files will make the disk access much more random, and make the disk performance much more weak. You mentioned that to increase overall IO cpapcity, one will have to use multiple spindles with sufficiently fast disk speed, but will it be more effective for the disk with fewer files? Or does the num of files is not an important factor for the entire performance of Kafka? Thanks again. xiaobinshe 2014-10-23 22:01 GMT+08:00 Todd Palino tpal...@gmail.com: Your understanding of RAID 10 is slightly off. Because it is a combination of striping and mirroring, trying to say that there are 4000 open files per pair of disks is not accurate. The disk, as far as the system is concerned, is the entire RAID. Files are striped across all mirrors, so any open file will cross all 7 mirror sets. Even if you were to operate on a single disk, you're never going to be able to ensure sequential disk access with Kafka. Even if you have a single partition on a disk, there will be multiple log files for that partition and you will have to seek to read older data. What you have to do is use multiple spindles, with sufficiently fast disk speeds, to increase your overall IO capacity. You can also tune to get a little more. For example, we use a 120 second commit on that mount point to reduce the frequency of flushing to disk. -Todd On Wed, Oct 22, 2014 at 10:09 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
Hmm, I haven't read the design doc lately, but I'm surprised that there's even a discussion of sequential disk access. I suppose for small subsets of the writes you can write larger blocks of sequential data, but that's about the extent of it. Maybe one of the developers can speak more to that aspect. As far as the number of files goes, it really doesn't matter that much whether you have a few or a lot. Once you have more than one, the disk access is random, so the performance is more like a cliff than a gentle slope. As I said, we've found issues once we go above 4000 partitions, and that's probably a combination of what the software can handle and the number of open files. -Todd On Thu, Oct 23, 2014 at 11:19 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you very much for your reply. My understanding of RAID 10 is wrong. I understand that one can not get absolute sequential disk access even on one single disk, the reason I'm interested with this question is that the design document of Kafka emphasize that Kafka make advantage of the sequential disk acceess to improve the disk performance, and I can' t understand how to achive this with thounds of open files. I thought that compare to one or fewer files, thounds of open files will make the disk access much more random, and make the disk performance much more weak. You mentioned that to increase overall IO cpapcity, one will have to use multiple spindles with sufficiently fast disk speed, but will it be more effective for the disk with fewer files? Or does the num of files is not an important factor for the entire performance of Kafka? Thanks again. xiaobinshe 2014-10-23 22:01 GMT+08:00 Todd Palino tpal...@gmail.com: Your understanding of RAID 10 is slightly off. Because it is a combination of striping and mirroring, trying to say that there are 4000 open files per pair of disks is not accurate. The disk, as far as the system is concerned, is the entire RAID. Files are striped across all mirrors, so any open file will cross all 7 mirror sets. Even if you were to operate on a single disk, you're never going to be able to ensure sequential disk access with Kafka. Even if you have a single partition on a disk, there will be multiple log files for that partition and you will have to seek to read older data. What you have to do is use multiple spindles, with sufficiently fast disk speeds, to increase your overall IO capacity. You can also tune to get a little more. For example, we use a 120 second commit on that mount point to reduce the frequency of flushing to disk. -Todd On Wed, Oct 22, 2014 at 10:09 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
Todd, Did you load-test using SSDs? Got numbers to share? On Fri, Oct 24, 2014 at 10:40 AM, Todd Palino tpal...@gmail.com wrote: Hmm, I haven't read the design doc lately, but I'm surprised that there's even a discussion of sequential disk access. I suppose for small subsets of the writes you can write larger blocks of sequential data, but that's about the extent of it. Maybe one of the developers can speak more to that aspect. As far as the number of files goes, it really doesn't matter that much whether you have a few or a lot. Once you have more than one, the disk access is random, so the performance is more like a cliff than a gentle slope. As I said, we've found issues once we go above 4000 partitions, and that's probably a combination of what the software can handle and the number of open files. -Todd On Thu, Oct 23, 2014 at 11:19 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you very much for your reply. My understanding of RAID 10 is wrong. I understand that one can not get absolute sequential disk access even on one single disk, the reason I'm interested with this question is that the design document of Kafka emphasize that Kafka make advantage of the sequential disk acceess to improve the disk performance, and I can' t understand how to achive this with thounds of open files. I thought that compare to one or fewer files, thounds of open files will make the disk access much more random, and make the disk performance much more weak. You mentioned that to increase overall IO cpapcity, one will have to use multiple spindles with sufficiently fast disk speed, but will it be more effective for the disk with fewer files? Or does the num of files is not an important factor for the entire performance of Kafka? Thanks again. xiaobinshe 2014-10-23 22:01 GMT+08:00 Todd Palino tpal...@gmail.com: Your understanding of RAID 10 is slightly off. Because it is a combination of striping and mirroring, trying to say that there are 4000 open files per pair of disks is not accurate. The disk, as far as the system is concerned, is the entire RAID. Files are striped across all mirrors, so any open file will cross all 7 mirror sets. Even if you were to operate on a single disk, you're never going to be able to ensure sequential disk access with Kafka. Even if you have a single partition on a disk, there will be multiple log files for that partition and you will have to seek to read older data. What you have to do is use multiple spindles, with sufficiently fast disk speeds, to increase your overall IO capacity. You can also tune to get a little more. For example, we use a 120 second commit on that mount point to reduce the frequency of flushing to disk. -Todd On Wed, Oct 22, 2014 at 10:09 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
We haven't done any testing of Kafka on SSDs, mostly because our storage density needs are too high. Since our IO load has been fine on the current model, we haven't pushed in that direction yet. Additionally, I haven't done any real load testing since I got here, which is part of why we're going to reevaluate our storage soon. That said, we are using SSDs for the transaction log volume on our Zookeeper nodes, with great success. We detailed some of that in the presentation that Jonathan linked (no latency or outstanding requests). It helps that we use very high quality SSD drives. -Todd On Fri, Oct 24, 2014 at 10:44 AM, Gwen Shapira gshap...@cloudera.com wrote: Todd, Did you load-test using SSDs? Got numbers to share? On Fri, Oct 24, 2014 at 10:40 AM, Todd Palino tpal...@gmail.com wrote: Hmm, I haven't read the design doc lately, but I'm surprised that there's even a discussion of sequential disk access. I suppose for small subsets of the writes you can write larger blocks of sequential data, but that's about the extent of it. Maybe one of the developers can speak more to that aspect. As far as the number of files goes, it really doesn't matter that much whether you have a few or a lot. Once you have more than one, the disk access is random, so the performance is more like a cliff than a gentle slope. As I said, we've found issues once we go above 4000 partitions, and that's probably a combination of what the software can handle and the number of open files. -Todd On Thu, Oct 23, 2014 at 11:19 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you very much for your reply. My understanding of RAID 10 is wrong. I understand that one can not get absolute sequential disk access even on one single disk, the reason I'm interested with this question is that the design document of Kafka emphasize that Kafka make advantage of the sequential disk acceess to improve the disk performance, and I can' t understand how to achive this with thounds of open files. I thought that compare to one or fewer files, thounds of open files will make the disk access much more random, and make the disk performance much more weak. You mentioned that to increase overall IO cpapcity, one will have to use multiple spindles with sufficiently fast disk speed, but will it be more effective for the disk with fewer files? Or does the num of files is not an important factor for the entire performance of Kafka? Thanks again. xiaobinshe 2014-10-23 22:01 GMT+08:00 Todd Palino tpal...@gmail.com: Your understanding of RAID 10 is slightly off. Because it is a combination of striping and mirroring, trying to say that there are 4000 open files per pair of disks is not accurate. The disk, as far as the system is concerned, is the entire RAID. Files are striped across all mirrors, so any open file will cross all 7 mirror sets. Even if you were to operate on a single disk, you're never going to be able to ensure sequential disk access with Kafka. Even if you have a single partition on a disk, there will be multiple log files for that partition and you will have to seek to read older data. What you have to do is use multiple spindles, with sufficiently fast disk speeds, to increase your overall IO capacity. You can also tune to get a little more. For example, we use a 120 second commit on that mount point to reduce the frequency of flushing to disk. -Todd On Wed, Oct 22, 2014 at 10:09 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is
Re: How many partition can one single machine handle in Kafka?
I've been thinking about this recently. If kafka provided cmdline hooks to be executed on segment rotation, similar to postgres' wal 'archive_command', configurations could store only the current segments and all their random i/o on flash, then once rotated, copy them sequentially onto larger/slower spinning disks, or even S3. -neil On Wed, Oct 22, 2014 at 10:09 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
I've mentioned this a couple times in discussions recently as well. We were discussing the concept of infinite retention for a certain type of service, and how it might be accomplished. My suggestion was to have a combination of storage types and the ability for Kafka to look for segments in two different directory structures. This way you could expand the backend storage as needed (which could be on an external storage appliance) while still maintaining performance for recent segments. I still think this is something worth pursuing at some point, and it should be relatively easy to implement within the broker. -Todd On Wed, Oct 22, 2014 at 11:53 PM, Neil Harkins nhark...@gmail.com wrote: I've been thinking about this recently. If kafka provided cmdline hooks to be executed on segment rotation, similar to postgres' wal 'archive_command', configurations could store only the current segments and all their random i/o on flash, then once rotated, copy them sequentially onto larger/slower spinning disks, or even S3. -neil On Wed, Oct 22, 2014 at 10:09 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
This is actually a very vague statement and does not cover every use case. Having a RAID10 array of 6x250G SSDs is very different from having 4x1T spinning drives. In my experience rebuilding a raid10 array that has several smaller SSD disks is hardly noticeable from the service point of view, because the IO write load is distributed amongst several disk pairs. You get lets say 1/2...1/4 (depending how many disk pairs you have) of the per node IO bandwidth. What configuration have you had the experience with? Was it fewer spinning disks? Regards, Istvan On Wed, Oct 22, 2014 at 3:44 PM, Neha Narkhede neha.narkh...@gmail.com wrote: In my experience, RAID 10 doesn't really provide value in the presence of replication. When a disk fails, the RAID resync process is so I/O intensive that it renders the broker useless until it completes. When this happens, you actually have to take the broker out of rotation and move the leaders off of it to prevent it from serving requests in a degraded state. You might as well shutdown the broker, delete the broker's data and let it catch up from the leader. On Wed, Oct 22, 2014 at 11:20 AM, Gwen Shapira gshap...@cloudera.com wrote: Makes sense. Thanks :) On Wed, Oct 22, 2014 at 11:10 AM, Jonathan Weeks jonathanbwe...@gmail.com wrote: There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall smoother operation. Best Regards, -Jonathan On Oct 22, 2014, at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe -- the sun shines for all
Re: How many partition can one single machine handle in Kafka?
RAID has nothing to do with the overall availability of your system, it is just increasing the per node reliability. Regards, Istvan On Wed, Oct 22, 2014 at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe -- the sun shines for all
Re: How many partition can one single machine handle in Kafka?
The number of brokers doesn't really matter here, as far as I can tell, because the question is about what a single broker can handle. The number of partitions in the cluster is governed by the ability of the controller to manage the list of partitions for the cluster, and the ability of each broker to keep that list (to serve metadata requests). The number of partitions on a single broker is governed by that broker's ability to handle the messages and files on disk. That's a much more limiting factor than what the controller can do. -Todd On Tue, Oct 21, 2014 at 2:52 PM, Neil Harkins nhark...@gmail.com wrote: On Tue, Oct 21, 2014 at 2:10 PM, Todd Palino tpal...@gmail.com wrote: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. How many brokers? I'm curious: what kinds of problems would affect a single broker with a large number of partitions, but not affect the entire cluster with even more partitions?
Re: How many partition can one single machine handle in Kafka?
In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall smoother operation. Best Regards, -Jonathan On Oct 22, 2014, at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
Makes sense. Thanks :) On Wed, Oct 22, 2014 at 11:10 AM, Jonathan Weeks jonathanbwe...@gmail.com wrote: There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall smoother operation. Best Regards, -Jonathan On Oct 22, 2014, at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
In my experience, RAID 10 doesn't really provide value in the presence of replication. When a disk fails, the RAID resync process is so I/O intensive that it renders the broker useless until it completes. When this happens, you actually have to take the broker out of rotation and move the leaders off of it to prevent it from serving requests in a degraded state. You might as well shutdown the broker, delete the broker's data and let it catch up from the leader. On Wed, Oct 22, 2014 at 11:20 AM, Gwen Shapira gshap...@cloudera.com wrote: Makes sense. Thanks :) On Wed, Oct 22, 2014 at 11:10 AM, Jonathan Weeks jonathanbwe...@gmail.com wrote: There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall smoother operation. Best Regards, -Jonathan On Oct 22, 2014, at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
Neha, Do you mean RAID 10 or RAID 5 or 6? With RAID 5 or 6, recovery is definitely very painful, but less so with RAID 10. We have been using the guidance here: http://www.youtube.com/watch?v=19DvtEC0EbQ#t=190 (LinkedIn Site Reliability Engineers state they run RAID 10 on all Kafka clusters @34:40 or so) Plus: https://cwiki.apache.org/confluence/display/KAFKA/Operations LinkedIn Hardware We are using dual quad-core Intel Xeon machines with 24GB of memory. In general this should not matter too much, we only see pretty low CPU usage at peak even with GZIP compression enabled and a number of clients that don't batch requests. The memory is probably more than is needed for caching the active segments of the log. The disk throughput is important. We have 8x7200 rpm SATA drives in a RAID 10 array. In general this is the performance bottleneck, and more disks is more better. Depending on how you configure flush behavior you may or may not benefit from more expensive disks (if you flush often then higher RPM SAS drives may be better). OS Settings We use Linux. Ext4 is the filesystem and we run using software RAID 10. We haven't benchmarked filesystems so other filesystems may be superior. We have added two tuning changes: (1) we upped the number of file descriptors since we have lots of topics and lots of connections, and (2) we upped the max socket buffer size to enable high-performance data transfer between data centers (described here). Best Regards, -Jonathan On Oct 22, 2014, at 3:44 PM, Neha Narkhede neha.narkh...@gmail.com wrote: In my experience, RAID 10 doesn't really provide value in the presence of replication. When a disk fails, the RAID resync process is so I/O intensive that it renders the broker useless until it completes. When this happens, you actually have to take the broker out of rotation and move the leaders off of it to prevent it from serving requests in a degraded state. You might as well shutdown the broker, delete the broker's data and let it catch up from the leader. On Wed, Oct 22, 2014 at 11:20 AM, Gwen Shapira gshap...@cloudera.com wrote: Makes sense. Thanks :) On Wed, Oct 22, 2014 at 11:10 AM, Jonathan Weeks jonathanbwe...@gmail.com wrote: There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall smoother operation. Best Regards, -Jonathan On Oct 22, 2014, at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
Yeah, Jonathan, I'm the LinkedIn SRE who said that :) And Neha, up until recently, sat 8 feet from my desk. The data from the wiki page is off a little bit as well (we're running 14 disks now, and 64 GB systems) So to hit the first questions, RAID 10 gives higher read performance, and also allows you to suffer a disk failure without having to drop the entire cluster. As Neha noted, you're going to take a hit on the rebuild, and because of ongoing traffic in the cluster it will be for a long time (we can easily take half a day to rebuild a disk). But you still get some benefit out of the RAID over just killing the data and letting it rebuild from the replica, because during that time the cluster is not under replicated, so you can suffer another failure. The more servers and disks you have, the more often disks are going to fail, not to mention other components. Both hardware and software. I like running on the safer side. That said, I'm not sure RAID 10 is the answer either. We're going to be doing some experimenting with other disk layouts shortly. We've inherited a lot of our architecture, and many things have changed in that time. We're probably going to test out RAID 5 and 6 to start with and see how much we lose from the parity calculations. -Todd On Wed, Oct 22, 2014 at 3:59 PM, Jonathan Weeks jonathanbwe...@gmail.com wrote: Neha, Do you mean RAID 10 or RAID 5 or 6? With RAID 5 or 6, recovery is definitely very painful, but less so with RAID 10. We have been using the guidance here: http://www.youtube.com/watch?v=19DvtEC0EbQ#t=190 (LinkedIn Site Reliability Engineers state they run RAID 10 on all Kafka clusters @34:40 or so) Plus: https://cwiki.apache.org/confluence/display/KAFKA/Operations LinkedIn Hardware We are using dual quad-core Intel Xeon machines with 24GB of memory. In general this should not matter too much, we only see pretty low CPU usage at peak even with GZIP compression enabled and a number of clients that don't batch requests. The memory is probably more than is needed for caching the active segments of the log. The disk throughput is important. We have 8x7200 rpm SATA drives in a RAID 10 array. In general this is the performance bottleneck, and more disks is more better. Depending on how you configure flush behavior you may or may not benefit from more expensive disks (if you flush often then higher RPM SAS drives may be better). OS Settings We use Linux. Ext4 is the filesystem and we run using software RAID 10. We haven't benchmarked filesystems so other filesystems may be superior. We have added two tuning changes: (1) we upped the number of file descriptors since we have lots of topics and lots of connections, and (2) we upped the max socket buffer size to enable high-performance data transfer between data centers (described here). Best Regards, -Jonathan On Oct 22, 2014, at 3:44 PM, Neha Narkhede neha.narkh...@gmail.com wrote: In my experience, RAID 10 doesn't really provide value in the presence of replication. When a disk fails, the RAID resync process is so I/O intensive that it renders the broker useless until it completes. When this happens, you actually have to take the broker out of rotation and move the leaders off of it to prevent it from serving requests in a degraded state. You might as well shutdown the broker, delete the broker's data and let it catch up from the leader. On Wed, Oct 22, 2014 at 11:20 AM, Gwen Shapira gshap...@cloudera.com wrote: Makes sense. Thanks :) On Wed, Oct 22, 2014 at 11:10 AM, Jonathan Weeks jonathanbwe...@gmail.com wrote: There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall smoother operation. Best Regards, -Jonathan On Oct 22, 2014, at 11:01 AM, Gwen Shapira gshap...@cloudera.com wrote: RAID-10? Interesting choice for a system where the data is already replicated between nodes. Is it to avoid the cost of large replication over the network? how large are these disks? On Wed, Oct 22, 2014 at 10:00 AM, Todd Palino tpal...@gmail.com wrote: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will
Re: How many partition can one single machine handle in Kafka?
I suppose it also is going to depend on: a) How much spare I/O bandwidth the brokers have as well to support a rebuild while supporting ongoing requests. Our brokers have spare IO capacity. b) How many brokers are in the cluster and what the replication factor is — e.g. if you have a larger cluster, it is easier to tolerate the loss of a single broker. We started with 3 brokers, so the loss of a single broker is quite significant — we would prefer possibly degraded performance to having a “down” broker. I do understand that y’all both work at LinkedIn, my point is that all of the guidance to date (as recently as this summer) is that in production LinkedIn runs on RAID 10, so it is just a bit odd to hear a contrary recommendation, although I do understand that best practices are a moving, evolving target. Best Regards, -Jonathan On Oct 22, 2014, at 4:05 PM, Todd Palino tpal...@gmail.com wrote: Yeah, Jonathan, I'm the LinkedIn SRE who said that :) And Neha, up until recently, sat 8 feet from my desk. The data from the wiki page is off a little bit as well (we're running 14 disks now, and 64 GB systems) So to hit the first questions, RAID 10 gives higher read performance, and also allows you to suffer a disk failure without having to drop the entire cluster. As Neha noted, you're going to take a hit on the rebuild, and because of ongoing traffic in the cluster it will be for a long time (we can easily take half a day to rebuild a disk). But you still get some benefit out of the RAID over just killing the data and letting it rebuild from the replica, because during that time the cluster is not under replicated, so you can suffer another failure. The more servers and disks you have, the more often disks are going to fail, not to mention other components. Both hardware and software. I like running on the safer side. That said, I'm not sure RAID 10 is the answer either. We're going to be doing some experimenting with other disk layouts shortly. We've inherited a lot of our architecture, and many things have changed in that time. We're probably going to test out RAID 5 and 6 to start with and see how much we lose from the parity calculations. -Todd On Wed, Oct 22, 2014 at 3:59 PM, Jonathan Weeks jonathanbwe...@gmail.com wrote: Neha, Do you mean RAID 10 or RAID 5 or 6? With RAID 5 or 6, recovery is definitely very painful, but less so with RAID 10. We have been using the guidance here: http://www.youtube.com/watch?v=19DvtEC0EbQ#t=190 (LinkedIn Site Reliability Engineers state they run RAID 10 on all Kafka clusters @34:40 or so) Plus: https://cwiki.apache.org/confluence/display/KAFKA/Operations LinkedIn Hardware We are using dual quad-core Intel Xeon machines with 24GB of memory. In general this should not matter too much, we only see pretty low CPU usage at peak even with GZIP compression enabled and a number of clients that don't batch requests. The memory is probably more than is needed for caching the active segments of the log. The disk throughput is important. We have 8x7200 rpm SATA drives in a RAID 10 array. In general this is the performance bottleneck, and more disks is more better. Depending on how you configure flush behavior you may or may not benefit from more expensive disks (if you flush often then higher RPM SAS drives may be better). OS Settings We use Linux. Ext4 is the filesystem and we run using software RAID 10. We haven't benchmarked filesystems so other filesystems may be superior. We have added two tuning changes: (1) we upped the number of file descriptors since we have lots of topics and lots of connections, and (2) we upped the max socket buffer size to enable high-performance data transfer between data centers (described here). Best Regards, -Jonathan On Oct 22, 2014, at 3:44 PM, Neha Narkhede neha.narkh...@gmail.com wrote: In my experience, RAID 10 doesn't really provide value in the presence of replication. When a disk fails, the RAID resync process is so I/O intensive that it renders the broker useless until it completes. When this happens, you actually have to take the broker out of rotation and move the leaders off of it to prevent it from serving requests in a degraded state. You might as well shutdown the broker, delete the broker's data and let it catch up from the leader. On Wed, Oct 22, 2014 at 11:20 AM, Gwen Shapira gshap...@cloudera.com wrote: Makes sense. Thanks :) On Wed, Oct 22, 2014 at 11:10 AM, Jonathan Weeks jonathanbwe...@gmail.com wrote: There are various costs when a broker fails, including broker leader election for each partition, etc., as well as exposing possible issues for in-flight messages, and client rebalancing etc. So even though replication provides partition redundancy, RAID 10 on each broker is usually a good tradeoff to prevent the typical most common cause of broker server failure (e.g. disk failure) as well, and overall
Re: How many partition can one single machine handle in Kafka?
Todd, Thank you for the information. With 28,000+ files and 14 disks, that makes there are averagely about 4000 open files on two disk ( which is treated as one single disk) , am I right? How do you manage to make the all the write operation to thest 4000 open files be sequential to the disk? As far as I know, write operation to different files on the same disk will cause random write, which is not good for performance. xiaobinshe 2014-10-23 1:00 GMT+08:00 Todd Palino tpal...@gmail.com: In fact there are many more than 4000 open files. Many of our brokers run with 28,000+ open files (regular file handles, not network connections). In our case, we're beefing up the disk performance as much as we can by running in a RAID-10 configuration with 14 disks. -Todd On Tue, Oct 21, 2014 at 7:58 PM, Xiaobin She xiaobin...@gmail.com wrote: Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
How many partition can one single machine handle in Kafka?
hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
Xiaobin, This FAQ may give you some hints: https://cwiki.apache.org/confluence/display/KAFKA/FAQ#FAQ-HowdoIchoosethenumberofpartitionsforatopic ? On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe -- -- Guozhang
Re: How many partition can one single machine handle in Kafka?
As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
Re: How many partition can one single machine handle in Kafka?
On Tue, Oct 21, 2014 at 2:10 PM, Todd Palino tpal...@gmail.com wrote: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. How many brokers? I'm curious: what kinds of problems would affect a single broker with a large number of partitions, but not affect the entire cluster with even more partitions?
Re: How many partition can one single machine handle in Kafka?
Todd, Actually I'm wondering how kafka handle so much partition, with one partition there is at least one file on disk, and with 4000 partition, there will be at least 4000 files. When all these partitions have write request, how did Kafka make the write operation on the disk to be sequential (which is emphasized in the design document of Kafka) and make sure the disk access is effective? Thank you for your reply. xiaobinshe 2014-10-22 5:10 GMT+08:00 Todd Palino tpal...@gmail.com: As far as the number of partitions a single broker can handle, we've set our cap at 4000 partitions (including replicas). Above that we've seen some performance and stability issues. -Todd On Tue, Oct 21, 2014 at 12:15 AM, Xiaobin She xiaobin...@gmail.com wrote: hello, everyone I'm new to kafka, I'm wondering what's the max num of partition can one siggle machine handle in Kafka? Is there an sugeest num? Thanks. xiaobinshe
