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From "Josh Elser (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-2842) Allow for use of hflush instead of hsync
Date Tue, 17 Jun 2014 15:25:39 GMT


Josh Elser commented on ACCUMULO-2842:

Orthogonal for the most part. I believe this will only save you when you're closing the file
(e.g. a WAL), not the incremental syncs that we expect to happen after we have updated entries
in the metadata table, for example. If you have some power outage without using {{hsync}}
before we close a file (which, remember, happens when we hit that max WAL size), I do not
believe {{dfs.datanode.synconclose}} does anything for you.

I think you could say this would be a middle ground between {{hflush}} everything, {{hflush}}
normally but {{(h)sync}} on close, and {{hsync}} everything, but I would want to re-read some
datanode code before you quote that :)

> Allow for use of hflush instead of hsync
> ----------------------------------------
>                 Key: ACCUMULO-2842
>                 URL:
>             Project: Accumulo
>          Issue Type: Improvement
>          Components: logger
>            Reporter: Josh Elser
>            Assignee: Josh Elser
>             Fix For: 1.5.2, 1.6.1, 1.7.0
> We keep getting onto the discussion on hsync versus hflush performance; however, we lack
a way to actually test this.
> Make the invocation of hflush or hsync configurable. It should not change the default,
so users on existing major releases should not be affected unless they choose to change their

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