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From Ramu M S <ramu.ma...@gmail.com>
Subject HBase Random Read latency > 100ms
Date Mon, 07 Oct 2013 05:01:16 GMT
Hi All,

My HBase cluster has 8 Region Servers (CDH 4.4.0, HBase 0.94.6).

Each Region Server is with the following configuration,
16 Core CPU, 192 GB RAM, 800 GB SATA (7200 RPM) Disk
(Unfortunately configured with RAID 1, can't change this as the Machines
are leased temporarily for a month).

I am running YCSB benchmark tests on HBase and currently inserting around
1.8 Billion records.
(1 Key + 7 Fields of 100 Bytes = 724 Bytes per record)

Currently I am getting a write throughput of around 100K OPS, but random
reads are very very slow, all gets have more than 100ms or more latency.

I have changed the following default configuration,
1. HFile Size: 16GB
2. HDFS Block Size: 512 MB

Total Data size is around 1.8 TB (Excluding the replicas).
My Table is split into 128 Regions (No pre-splitting used, started with 1
and grew to 128 over the insertion time)

Taking some inputs from earlier discussions I have done the following
changes to disable Nagle (In both Client and Server hbase-site.xml,



Ganglia stats shows large CPU IO wait (>30% during reads).

I agree that disk configuration is not ideal for Hadoop cluster, but as
told earlier it can't change for now.
I feel the latency is way beyond any reported results so far.

Any pointers on what can be wrong?


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