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https://issues.apache.org/jira/browse/ACCUMULO-4146?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Keith Turner updated ACCUMULO-4146:
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Attachment: screenshot-1.png
> Per-durability write-ahead logs
> -------------------------------
>
> Key: ACCUMULO-4146
> URL: https://issues.apache.org/jira/browse/ACCUMULO-4146
> Project: Accumulo
> Issue Type: Improvement
> Reporter: Christopher Tubbs
> Fix For: 1.8.0
>
> Attachments: screenshot-1.png
>
>
> [~kturner] showed me a scenario with Continuous Ingest, where the system was
> configured to use "flush" for it's durability, but the Metadata table was
> configured to use "sync" (default for metadata). When the system grew large
> enough to have many tablets, lots of tablets were constantly writing to the
> metadata table on a relatively few number of tablet servers. This caused all
> ingest to drop to 0 very frequently as the tables waiting on a "flush" had to
> wait for the WAL to "sync".
> This problem is primarily caused by the fact that we have only one WAL per
> tablet server, and so tablet writes waiting on a flush had to wait on a sync
> if any concurrent write to the tablet server required a sync.
> We could possibly alleviate this problem if we permitted tablet servers to
> have multiple WALs open. One potentially good way to manage these multiple
> WALs is to group them by durability, so there'd be one WAL for sync, and
> another for flush. That way, writes requiring a flush would not wait on
> sync's.
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