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HBase, mail # user - What could cause HBase's writes slower than reads?


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yun peng 2012-11-03, 04:07
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Mohit Anchlia 2012-11-03, 05:04
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yun peng 2012-11-03, 14:09
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Re: What could cause HBase's writes slower than reads?
Mohit Anchlia 2012-11-03, 15:11
Some of the things to look at is I/O on the disk, CPU on the server. Look
at CPU and java thread dumps on the client. I use Ganglia to look at server
stats and it is often very helpful.

In my opinon best thing would be to add some code around various HBase
calls to see where time is being spent on the client side and then go from
there.

Do your reads read same data set as writes?

On Sat, Nov 3, 2012 at 7:09 AM, yun peng <[EMAIL PROTECTED]> wrote:

> Hi, the throughput for write-only workload is 450 ops/sec and for read-only
> 900 ops/sec. I am using the same machine (1-core CPU, 2G mem) for client to
> drive workload into hbase/hdfs... one thread is used in client side. For
> this workload, it looks client should not be the bottleneck... Btw, is
> there anyway to verify this.
> Thanks,
> Yun
>
> On Sat, Nov 3, 2012 at 1:04 AM, Mohit Anchlia <[EMAIL PROTECTED]
> >wrote:
>
> > What load do you see on the system? I am wondering if bottleneck is on
> the
> > client side.
> >
> > On Fri, Nov 2, 2012 at 9:07 PM, yun peng <[EMAIL PROTECTED]> wrote:
> >
> > > Hi, All,
> > > In my HBase cluster, I observed Put() executes faster than a Get().
> Since
> > > HBase is optimized towards write, I wonder what may affect Put
> > performance
> > > in a distributed setting below.
> > >
> > > Hbase setup:
> > > My HBase cluster are of three nodes, in which one hosts zookeeper and
> > > HMaster, and two slaves. HBase cluster is attached to HDFS which
> resides
> > on
> > > a separated cluster. The machines are fairly commodity or lower end,
> with
> > > 2G memory and 1-core CPU.
> > >
> > > Observed results:
> > > I test the Put and Get latency on this setup, and find out Put runs
> > slower
> > > than Get (which is a bit surprising to me.) In case anyone is
> interested,
> > > in my result, Put() takes around 3000us and Get only in 1000us (so I
> > think
> > > it does not touch disk).
> > >
> > > What could possibly slow dow Put() and speed up Get() performance in
> > HBase?
> > > Does this possibly have to do with distributed setting, like Put needs
> > > update multiple (duplicated) copies while Gets only one..  I am quite
> > > newbie to HBase internal and not familiar with HBase Put/Get code path,
> > has
> > > anyone here have similar experiences?
> > >
> > > Thanks,
> > > Yun
> > >
> >
>
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yun peng 2012-11-04, 15:08