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From Ryan Rawson <ryano...@gmail.com>
Subject Re: master performance
Date Tue, 02 Jun 2009 00:48:52 GMT

The issue actually isn't with Master performance, but the performance of
scanning .META. which is done for every single UI load.  I'm not sure there
are any good answers for 0.19.x...

However, once it becomes available, HBase 0.20.0 will answer some of these
for you.  A combination of improved scanners, block caching, LZO-based
compression and other fixes should make HBase much more snappy.

This is obviously not the best answer, but there is a roadmap out of the

Good luck!

On Mon, Jun 1, 2009 at 5:31 PM, Jeremy Pinkham <jeremy@lotame.com> wrote:

> sorry for the novel...
> I've been experiencing some problems with my hbase cluster and hoping
> someone can point me in the right direction.  I have a 40 node cluster
> running 0.19.0.  Each node has 4 cores, 8GB (2GB dedicated to the
> regionserver), and 1TB data disk.  The master is on a dedicated machine
> separate from the namenode and the jobtracker.  There is a single table with
> 4 column families and 3700 regions evenly spread across the 40 nodes.  The
> TTL's match our loading pace well enough that we don't typically see too
> many splits anymore.
> In trying to troubleshoot some larger issues with bulk loads on this
> cluster I have created a test scenario to try and narrow the problem based
> on various symptoms.  This test is map/reduce job that is using the
> HRegionPartitioner (as an easy way to generate some traffic to the master
> for meta data).  I've been running this job with various size inputs to
> gauge the effect of different numbers of mappers and have found that as the
> number of concurrent mappers creeps up to what I think are still small
> numbers (<50 mappers), the performance of the master is dramatically
> impacted.  I'm judging the performance here simply by checking the response
> time of the UI on the master, since that has historically been a good
> indication of when the cluster is getting into trouble during our loads
> (which I'm sure could mean a lot of things), although i suppose it's
> possible to two are unrelated.
> The UI normally takes about 5-7 seconds to refresh master.jsp.  Running a
> job with 5 mappers doesn't seem to impact it too much, but a job with 38
> mappers makes the UI completely unresponsive for anywhere from 30 seconds to
> several minutes during the run.  During this time, there is nothing
> happening in the logs, scans/gets from within the shell continue to work
> fine, and ganglia/top show the box to be virtually idle.  All links off of
> master.jsp work fine, so I presume it's something about the master pulling
> info from the individual nodes, but those UI's are also perfectly
> responsive.
> This same cluster used to run on just 20 nodes without issue, so I'm
> curious if I've crossed some threshold of horizontal scalability or if there
> is just a tuning parameter that I'm missing that might take care of this, or
> if there is something known between 0.19.0 and 0.19.3 that might be a
> factor.
> Thanks
> jeremy
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