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From elsif <elsif.t...@gmail.com>
Subject Re: HBase Exceptions on version 0.20.1
Date Tue, 20 Oct 2009 23:47:43 GMT
The cpu load on each of the nodes never goes above 1 and very little if
any swap is in use.

The 4MB is our boundary case - the actual data will always be smaller. 
This was just a encapsulated test that reproduces our issue.

I will re-test with the CMS collector and logging enabled and reply back.

> Most of these exceptions look related to overloaded servers (GC pauses
> causing timeouts, high IO wait tripping up the datanodes, etc).  Have
> you turned on GC logging?  Also, are you swapping on these nodes?
> Check out the performance tuning page here:
> http://wiki.apache.org/hadoop/PerformanceTuning
> The WrongRegionException at the end could be a fault but it's hard to
> know without seeing the entire context and knowing what the cluster
> was up to at that point.
> Performance can degrade as the JVMs fill up, get more and more
> fragmented, and the GC gets slower.
> Also, you are inserting 4MB values?  Those are fairly large, at the
> upper-end of what you would want to put into HBase.  Is this your
> actual use case?  At the least you'll want to increase your region
> size (otherwise you're going to have at most 64 rows per region, often
> less), but also consider if HBase is the right place to store 4MB values.
> Hope that helps.
> JG

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