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From "Andrew Purtell (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-2821) Keep young storefiles at lower replication
Date Wed, 13 Aug 2014 17:28:11 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2821?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14095755#comment-14095755

Andrew Purtell commented on HBASE-2821:

bq. Maybe add another chore that after X amount of seconds it will automatically increase
the number of replicas to 3 (or user default).

That's in the patch

> 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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