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From Per Steffensen <st...@designware.dk>
Subject Re: HBase/HDFS very high iowait
Date Wed, 22 Feb 2012 10:19:40 GMT
Observe about 50% iowait before even starting clients - that is when 
there is actually no load from clients on the system. So only "internal" 
stuff in HBase/HDFS can cause this - HBase compaction? HDFS?

Regards, Per Steffensen

Per Steffensen skrev:
> Hi
> We have a system a.o. with a HBase cluster and a HDFS cluster 
> (primarily for HBase persistence). Depending on the environment we 
> have between 3 and 8 machine running a HBase RegionServer and a HDFS 
> DataNode. OS is Ubuntu 10.04. On those machine we see very high iowait 
> and very little "real usage" of the CPU, and unexpected low throughput 
> (HBase creates, updates, reads and short scans). We do not get more 
> throughput by putting more parallel load from the HBase clients on the 
> HBase servers, so it is a "real" iowait problem. Any idea what might 
> be wrong, and what we can do to improve throughput and lower iowait.
> Regards, Per Steffensen

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