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From "Jonathan Gray (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HBASE-2782) QOS for META table access
Date Thu, 24 Jun 2010 14:30:51 GMT

    [ https://issues.apache.org/jira/browse/HBASE-2782?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12882165#action_12882165
] 

Jonathan Gray commented on HBASE-2782:
--------------------------------------

Hmm, not sure I see the issues with moving META to ZK as snapshots and backups (these things
do not really exist today).  I also think mirroring META into ZK but retaining a table for
persistence could make good sense and also solve those issues, but let's not totally sidetrack
this jira.

I agree completely that we need to do work around QoS and what you're proposing makes sense
for META in the short-term and helps build towards QoS of user tables.  I'm still +1 on this
jira but think we should not limit this to a special-casing for META.

> QOS for META table access
> -------------------------
>
>                 Key: HBASE-2782
>                 URL: https://issues.apache.org/jira/browse/HBASE-2782
>             Project: HBase
>          Issue Type: Improvement
>          Components: regionserver
>            Reporter: Todd Lipcon
>
> I'd like to brainstorm some ideas on how we can prioritize reads and writes to META above
reads and writes to other tables. I've noticed that if the regionserver hosting META is under
heavy load, then lots of other operations take much longer than they should. For example,
I'm currently running 120 threads of YCSB across 3 client nodes hitting a 5-node cluster.
Doing a full scan of META (only 600 rows) takes upwards of 30 seconds in the shell, since
all of the handler threads are tied up and there's a long RPC queue. 

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