Hi Péter, Sounds like time to reassign the partitions you have across all the brokers/data dirs using the instructions from here https://kafka.apache.org/documentation/#basic_ops_automigrate. That assumes that your partition strategy has somewhat evenly filled your partitions and given it may move all the partitions it could be a bit intensive so be sure to use the throttle option. Cheers William
On 07/08/2020, Péter Nagykátai <st4r.f1...@gmail.com> wrote: > Hello everybody, > > Thank you for the detailed answers. My issue is partly answered here: > > > > > *This rule also applies to disk-level, which means that when a set > ofpartitions assigned to a specific broker, each of the disks will get > thesame number of partitions without considering the load of disks at > thattime.* > > I admit, I didn't provide enough info either. > > So my problem is that an existing topic got a huge surge of events for this > week. I knew that'll happen and I modified the partition count. > Unfortunately, it occurred to me a bit later, that I'll likely need some > extra disk space. So I added an extra disk to each broker. The thing I > didn't know, that Kafka won't evenly distribute the partitions on the > disks. > So the question still remains: > Is there any way to have Kafka evenly distribute data on its disks? > Also, what options do I have *after *I'm in the situation I described > above? (preferably without deleting the topic) > > Thanks! > > On Fri, Aug 7, 2020 at 12:00 PM Yingshuan Song <songyingsh...@gmail.com> > wrote: > >> Hi Peter, >> Agreed with Manoj and Vinicius, i think those rules led to this result : >> >> 1）the partitions of a topic - N and replication number - R determine the >> real partition-replica count of this topic, which is N * R; >> 2) kafka can distribute partitions evenly among brokers, but it is >> based >> on the broker count when the topic was created, this is important. >> If we create a topic (N - 4, R - 3) in a kafka cluster which contains 3 >> kafka brokers, then 4 * 3 / 3 = 4 partitions will be assigned to each >> broker. >> But if a new broker was added into this cluster and another topic (N - 4, >> R >> - 3) need to be created, then 4 * 3 / 4 = 3 partitions will be assigned >> to >> each broker. >> Kafka will not assign all those partitions to the new added broker even >> though it is idle and i think this is a shortcoming of kafka. >> This rule also applies to disk-level, which means that when a set of >> partitions assigned to a specific broker, each of the disks will get the >> same number of partitions without considering the load of disks at that >> time. >> 3） when producer send records to topics, how to chose partiton : 3-1) if >> a >> record has a key, then the partition number calculate according to the >> key; >> 3-2) if records have no keys, then those records will be sent to each >> partition in turns. So, if there are lots of records with the same key, >> and >> those records will be sent to the same partition, and may take up a lot >> of >> disk space. >> >> >> hope this helps >> >> Vinicius Scheidegger <vinicius.scheideg...@gmail.com> 于2020年8月7日周五 >> 上午6:10写道： >> >> > Hi Peter, >> > >> > AFAIK, everything depends on: >> > >> > 1) How you have configured your topic >> > a) number of partitions (here I understand you have 15 partitions) >> > b) partition replication configuration (each partition necessarily >> > has >> a >> > leader - primary responsible to hold the data - and for reads and >> > writes) >> > you can configure the topic to have a number of replicas >> > 2) How you publish messages to the topic >> > a) The publisher is responsible to choose the partition. This can be >> done >> > consciously (by setting the partition id while sending the message to >> > the >> > topic) or unconsciously (by using the DefaultPartitioner or any other >> > partitioner scheme). >> > >> > All messages sent to a specific partition will be written first to the >> > leader (meaning that the disk configured for the partition leader will >> > receive the load) and then replicated to the replica (followers). >> > Kafka does not automatically distribute the data equally to the >> > different >> > brokers - you need to think about your architecture having that in >> > mind. >> > >> > I hope it helps >> > >> > On Thu, Aug 6, 2020 at 10:23 PM Péter Nagykátai <st4r.f1...@gmail.com> >> > wrote: >> > >> > > I initially started with one data disk (mounted solely to hold Kafka >> > data) >> > > and recently added a new one. >> > > >> > > On Thu, Aug 6, 2020 at 10:13 PM <manoj.agraw...@cognizant.com> wrote: >> > > >> > > > What do you mean older disk ? >> > > > >> > > > On 8/6/20, 12:05 PM, "Péter Nagykátai" <st4r.f1...@gmail.com> >> wrote: >> > > > >> > > > [External] >> > > > >> > > > >> > > > Yeah, but it doesn't do that. My "older" disks have ~70 >> partitions, >> > > the >> > > > newer ones ~5 partitions. That's why I'm asking what went >> > > > wrong. >> > > > >> > > > On Thu, Aug 6, 2020 at 8:35 PM <manoj.agraw...@cognizant.com> >> > wrote: >> > > > >> > > > > Kafka evenly distributed number of partition on each disk so >> in >> > > > your case >> > > > > every disk should have 3/2 topic partitions . >> > > > > It is producer job to evenly produce data by partition key >> > > > to >> > > topic >> > > > > partition . >> > > > > How it partition key , it is auto generated or producer >> > > > sending >> > key >> > > > along >> > > > > with message . >> > > > > >> > > > > >> > > > > On 8/6/20, 7:29 AM, "Péter Nagykátai" <st4r.f1...@gmail.com> >> > > wrote: >> > > > > >> > > > > [External] >> > > > > >> > > > > >> > > > > Hello, >> > > > > >> > > > > I have a Kafka cluster with 3 brokers (v2.3.0) and each >> > broker >> > > > has 2 >> > > > > disks >> > > > > attached. I added a new topic (heavyweight) and was >> surprised >> > > > that >> > > > > even if >> > > > > the topic has 15 partitions, those weren't distributed >> evenly >> > > on >> > > > the >> > > > > disks. >> > > > > Thus I got one disk that's almost empty and the other >> almost >> > > > filled >> > > > > up. Is >> > > > > there any way to have Kafka evenly distribute data on its >> > > disks? >> > > > > >> > > > > Thank you! >> > > > > >> > > > > >> > > > > This e-mail and any files transmitted with it are for the >> > > > sole >> > use >> > > > of the >> > > > > intended recipient(s) and may contain confidential and >> privileged >> > > > > information. If you are not the intended recipient(s), please >> > reply >> > > > to the >> > > > > sender and destroy all copies of the original message. 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