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Posted to issues@hbase.apache.org by "Todd Lipcon (JIRA)" <ji...@apache.org> on 2010/07/07 19:52:54 UTC
[jira] Updated: (HBASE-2821) Keep young storefiles at lower
replication
[ https://issues.apache.org/jira/browse/HBASE-2821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Todd Lipcon updated HBASE-2821:
-------------------------------
Attachment: lifetime-distribution.png
Here's a plot of the file lifetimes from an overnight data import. You can see that most of the store files. Here's stats on the distribution:
Min. : 1
1st Qu.: 569
Median : 1353
Mean : 1801
3rd Qu.: 2526
Max. :13342
So, 25% of store files last less than 10 minutes, and half of them last less than 22 minutes.
> 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
> Attachments: lifetime-distribution.png
>
>
> 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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