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From "Jonathan Park (JIRA)" <>
Subject [jira] [Commented] (ACCUMULO-2801) define tablet syncs walog for each tablet in a batch
Date Tue, 10 Jun 2014 21:15:02 GMT


Jonathan Park commented on ACCUMULO-2801:


> define tablet syncs walog for each tablet in a batch
> ----------------------------------------------------
>                 Key: ACCUMULO-2801
>                 URL:
>             Project: Accumulo
>          Issue Type: Bug
>    Affects Versions: 1.5.0, 1.5.1, 1.6.0
>            Reporter: Keith Turner
> When the batch writer sends a batch of mutations for N tablets that were not currently
using a walog, then define tablet will be called for each tablet.  Define tablet will sync
the walog.   In hadoop 2 hsync is used, which is much slower than hadoop1 sync calls.  If
hsync takes 50ms and there are 100 tablets, then this operation would take 5 secs.  The calls
to define tablet do not occur frequently, just when walogs switch or tablets are loaded so
the cost will be amortized.  Ideally there could be one walog sync call for all of the tablets
in a batch of mutations.

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