RE: RAID or no RAID
With multiple data dirs you are still limited by the space free on any one drive. So if you have two data dirs with 40GB free on each, and you have 50GB to be compacted, it won't work, but if you had a raid, you would have 80GB free and could compact... -Original Message- From: mcasandra [mailto:mohitanch...@gmail.com] Sent: Tuesday, June 28, 2011 7:55 PM To: cassandra-u...@incubator.apache.org Subject: Re: RAID or no RAID aaron morton wrote: Not sure what the intended purpose is, but we've mostly used it as an emergency disk-capacity-increase option Thats what I've used it for. Cheers How does compaction work in terms of utilizing multiple data dirs? Also, is there a reference on wiki somewhere that says not to use multiple data dirs? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or -no-RAID-tp6522904p6527219.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: RAID or no RAID
aaron morton wrote: Not sure what the intended purpose is, but we've mostly used it as an emergency disk-capacity-increase option Thats what I've used it for. Cheers How does compaction work in terms of utilizing multiple data dirs? Also, is there a reference on wiki somewhere that says not to use multiple data dirs? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or-no-RAID-tp6522904p6527219.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: RAID or no RAID
RAID0 so you have one big volume. For performance (cassandra does not stripe sstables across the data dirs) and otherwise you'll have fragmentation and wont be able to utilise all your space. Cheers - Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 28 Jun 2011, at 11:46, mcasandra wrote: Which one is preferred RAID0 or spreading data files accross various disks on the same node? I like RAID0 but what would be the most convincing argument to put additional RAID controller card in the machine? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or-no-RAID-tp6522904p6522904.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: RAID or no RAID
If you have a quality HW raid controller with proper performance (and far from all have good performance) you cam definitely benefit from a battery backed up write cache on it, although the benefits will not be huge on raid 0. Unless you get a really good price on that high performance HW raid with battery backup, it is probably not worth it for raid 0. When that is said, raid 5 is pretty speedy as well with a good controller with battery cache so don't rule that out if you have the controller anyway and may save you from some manual recover operations.. Regards, Terje On 28 Jun 2011, at 08:46, mcasandra mohitanch...@gmail.com wrote: Which one is preferred RAID0 or spreading data files accross various disks on the same node? I like RAID0 but what would be the most convincing argument to put additional RAID controller card in the machine? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or-no-RAID-tp6522904p6522904.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: RAID or no RAID
I thought there is an option to give multiple data dirs in cassandra.yaml. What's the purpose of that? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or-no-RAID-tp6522904p6523523.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: RAID or no RAID
Not sure what the intended purpose is, but we've mostly used it as an emergency disk-capacity-increase option. It's not as good as raid because each disk size is counted individually (a compacted sstable can only be on one disk) so compaction size limits aren't expanded as one might expect. On Mon, Jun 27, 2011 at 11:30 PM, mcasandra mohitanch...@gmail.com wrote: I thought there is an option to give multiple data dirs in cassandra.yaml. What's the purpose of that? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or-no-RAID-tp6522904p6523523.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
Re: RAID or no RAID
Not sure what the intended purpose is, but we've mostly used it as an emergency disk-capacity-increase option Thats what I've used it for. Cheers - Aaron Morton Freelance Cassandra Developer @aaronmorton http://www.thelastpickle.com On 28 Jun 2011, at 15:55, Dan Kuebrich wrote: Not sure what the intended purpose is, but we've mostly used it as an emergency disk-capacity-increase option. It's not as good as raid because each disk size is counted individually (a compacted sstable can only be on one disk) so compaction size limits aren't expanded as one might expect. On Mon, Jun 27, 2011 at 11:30 PM, mcasandra mohitanch...@gmail.com wrote: I thought there is an option to give multiple data dirs in cassandra.yaml. What's the purpose of that? -- View this message in context: http://cassandra-user-incubator-apache-org.3065146.n2.nabble.com/RAID-or-no-RAID-tp6522904p6523523.html Sent from the cassandra-u...@incubator.apache.org mailing list archive at Nabble.com.
