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https://issues.apache.org/jira/browse/KAFKA-188?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jay Kreps updated KAFKA-188:
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Attachment: KAFKA-188-v4.patch
Attached an updated patch with a few very minor changes:
1. If there is only a single log directory I skip the least loaded calculation.
This calculation iterates over all logs so it could be a bit expensive in cases
where we have very many logs (though it should be rare). This makes it so that
the case where we have only one directory is no more expensive then it is now.
2. Fixed a deprecation warning
3. Fixed an outdated scaladoc comment
> Support multiple data directories
> ---------------------------------
>
> Key: KAFKA-188
> URL: https://issues.apache.org/jira/browse/KAFKA-188
> Project: Kafka
> Issue Type: New Feature
> Reporter: Jay Kreps
> Attachments: KAFKA-188.patch, KAFKA-188-v2.patch, KAFKA-188-v3.patch,
> KAFKA-188-v4.patch
>
>
> Currently we allow only a single data directory. This means that a multi-disk
> configuration needs to be a RAID array or LVM volume or something like that
> to be mounted as a single directory.
> For a high-throughput low-reliability configuration this would mean RAID0
> striping. Common wisdom in Hadoop land has it that a JBOD setup that just
> mounts each disk as a separate directory and does application-level balancing
> over these results in about 30% write-improvement. For example see this claim
> here:
> http://old.nabble.com/Re%3A-RAID-vs.-JBOD-p21466110.html
> It is not clear to me why this would be the case--it seems the RAID
> controller should be able to balance writes as well as the application so it
> may depend on the details of the setup.
> Nonetheless this would be really easy to implement, all you need to do is add
> multiple data directories and balance partition creation over these disks.
> One problem this might cause is if a particular topic is much larger than the
> others it might unbalance the load across the disks. The partition->disk
> assignment policy should probably attempt to evenly spread each topic to
> avoid this, rather than just trying keep the number of partitions balanced
> between disks.
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