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https://issues.apache.org/jira/browse/HBASE-2821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14095768#comment-14095768
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Andrew Purtell commented on HBASE-2821:
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bq. Interesting I wonder how much replica = 2 saves us with the default HDFS
settings (first copy local rack, 2nd copy other rack, 3rd copy other machine in
other rack). We only save a rack local copy.
Or change policy so first copy local, 2nd copy rack local, 3rd copy other rack,
and save on cross rack traffic. The expectation is within a rack we have full
bisectional bandwidth from any server to any other but the ToR switches are
oversubscribed.
> Keep young storefiles at lower replication
> ------------------------------------------
>
> Key: HBASE-2821
> URL: https://issues.apache.org/jira/browse/HBASE-2821
> Project: HBase
> Issue Type: Improvement
> Components: regionserver
> Reporter: Todd Lipcon
> Assignee: Andrew Purtell
> Fix For: 2.0.0
>
> Attachments: HBASE-2821.patch, lifetime-distribution.png,
> storefile_age.pl
>
>
> jgray and I were brainstorming some ideas about this:
> In a typical heavy-write scenario, many store files do not last very long.
> They're flushed and then within a small number of seconds a compaction runs
> and they get deleted. For these "short lifetime" store files, it's less
> likely that a failure will occur during the window in which they're valid.
> So, I think we can consider some optimizations like the following:
> - Flush files at replication count 2. Scan once a minute for any store files
> in the region that are older than 2 minutes. If they're found, increase their
> replication to 3. (alternatively, queue them to avoid scanning)
> - More dangerous: flush files at replication count 1, but don't count them
> when figuring log expiration. So, if they get lost, we force log splitting to
> recover.
> The performance gain here is that we avoid the network and disk transfer of
> writing the third replica for a file that we're just about to delete anyway.
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