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From "Stuart Scott" <Stuart.Sc...@e-mis.com>
Subject RE: Long client pauses with compression
Date Mon, 14 Mar 2011 05:19:40 GMT

We are experiencing the same issue. Have experimented with the memory
settings also but still get the same problem. We are inserting over
1,000,00 records. We find that it freezes as below but also, after
running for some time, the entire connectivity dies.
Would be interested in any progress on this one.



-----Original Message-----
From: Bryan Keller [mailto:bryanck@gmail.com] 
Sent: 13 March 2011 20:49
To: user@hbase.apache.org
Subject: Re: Long client pauses with compression

If interested, I wrote a small program that demonstrates the problem
(http://vancameron.net/HBaseInsert.zip). It uses Gradle, so you'll need
that. To run, enter "gradle run". 

On Mar 13, 2011, at 12:14 AM, Bryan Keller wrote:

> I am using the Java client API to write 10,000 rows with about 6000
columns each, via 8 threads making multiple calls to the
HTable.put(List<Put>) method. I start with an empty table with one
column family and no regions pre-created.
> With compression turned off, I am seeing very stable performance. At
the start there are a couple of 10-20sec  pauses where all insert
threads are blocked during a region split. Subsequent splits do not
cause all of the threads to block, presumably because there are more
regions so no one region split blocks all inserts. GCs for HBase during
the insert is not a major problem (6k/55sec).
> When using either LZO or gzip compression, however, I am seeing
frequent and long pauses, sometimes around 20 sec but often over 80
seconds in my test. During these pauses all 8 of the threads writing to
HBase are blocked. The pauses happen throughout the insert process. GCs
are higher in HBase when using compression (60k, 4min), but it doesn't
seem enough to explain these pauses. Overall performance obviously
suffers dramatically as a result (about 2x slower).
> I have tested this in different configurations (single node, 4 nodes)
with the same result. I'm using HBase 0.90.1 (CDH3B4), Sun/Oracle Java
1.6.0_24, CentOS 5.5, Hadoop LZO 0.4.10 from Cloudera. Machines have 12
cores and 24 gb of RAM. Settings are pretty much default, nothing out of
the ordinary. I tried playing around with region handler count and
memstore settings, but these had no effect.

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