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https://issues.apache.org/jira/browse/CASSANDRA-4292?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13422574#comment-13422574
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Jonathan Ellis commented on CASSANDRA-4292:
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bq. Directory is chosen based on available space in both queue and disk.
We still want to prioritize disks that have no tasks yet, since ipos are a
bigger bottleneck than space, in general.
So specifically, we want to prioritize in order of:
# enough space for the new sstable (boolean)
# zero tasks (boolean)
# total free space (long)
We may want to test changing #2 to ordering by task count... both have pros
and cons.
> Per-disk I/O queues
> -------------------
>
> Key: CASSANDRA-4292
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4292
> Project: Cassandra
> Issue Type: Improvement
> Components: Core
> Reporter: Jonathan Ellis
> Assignee: Yuki Morishita
> Fix For: 1.2
>
> Attachments: 4292-v2.txt, 4292.txt
>
>
> As noted in CASSANDRA-809, we have a certain amount of flush (and compaction)
> threads, which mix and match disk volumes indiscriminately. It may be worth
> creating a tight thread -> disk affinity, to prevent unnecessary conflict at
> that level.
> OTOH as SSDs become more prevalent this becomes a non-issue. Unclear how
> much pain this actually causes in practice in the meantime.
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