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HBase >> mail # user >> HBase Random Read latency > 100ms


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Re: HBase Random Read latency > 100ms
Quick questionon the disk side.

When you say:
800 GB SATA (7200 RPM) Disk
Is it 1x800GB? It's raid 1, so might be 2 drives? What's the configuration?

JM
2013/10/7 Ramu M S <[EMAIL PROTECTED]>

> Lars, Bharath,
>
> Compression is disabled for the table. This was not intended from the
> evaluation.
> I forgot to mention that during table creation. I will enable snappy and do
> major compaction again.
>
> Please suggest other options to try out and also suggestions for the
> previous questions.
>
> Thanks,
> Ramu
>
>
> On Mon, Oct 7, 2013 at 6:35 PM, Ramu M S <[EMAIL PROTECTED]> wrote:
>
> > Bharath,
> >
> > I was about to report this. Yes indeed there is too much of GC time.
> > Just verified the GC time using Cloudera Manager statistics(Every minute
> > update).
> >
> > For each Region Server,
> >  - During Read: Graph shows 2s constant.
> >  - During Compaction: Graph starts with 7s and goes as high as 20s during
> > end.
> >
> > Few more questions,
> > 1. For the current evaluation, since the reads are completely random and
> I
> > don't expect to read same data again can I set the Heap to the default 1
> GB
> > ?
> >
> > 2. Can I completely turn off BLOCK CACHE for this table?
> >     http://hbase.apache.org/book/regionserver.arch.html recommends that
> > for Randm reads.
> >
> > 3. But in the next phase of evaluation, We are interested to use HBase as
> > In-memory KV DB by having the latest data in RAM (To the tune of around
> 128
> > GB in each RS, we are setting up 50-100 Node Cluster). I am very curious
> to
> > hear any suggestions in this regard.
> >
> > Regards,
> > Ramu
> >
> >
> > On Mon, Oct 7, 2013 at 5:50 PM, Bharath Vissapragada <
> > [EMAIL PROTECTED]> wrote:
> >
> >> Hi Ramu,
> >>
> >> Thanks for reporting the results back. Just curious if you are hitting
> any
> >> big GC pauses due to block cache churn on such large heap. Do you see
> it ?
> >>
> >> - Bharath
> >>
> >>
> >> On Mon, Oct 7, 2013 at 1:42 PM, Ramu M S <[EMAIL PROTECTED]> wrote:
> >>
> >> > Lars,
> >> >
> >> > After changing the BLOCKSIZE to 16KB, the latency has reduced a
> little.
> >> Now
> >> > the average is around 75ms.
> >> > Overall throughput (I am using 40 Clients to fetch records) is around
> 1K
> >> > OPS.
> >> >
> >> > After compaction hdfsBlocksLocalityIndex is 91,88,78,90,99,82,94,97 in
> >> my 8
> >> > RS respectively.
> >> >
> >> > Thanks,
> >> > Ramu
> >> >
> >> >
> >> > On Mon, Oct 7, 2013 at 3:51 PM, Ramu M S <[EMAIL PROTECTED]>
> wrote:
> >> >
> >> > > Thanks Lars.
> >> > >
> >> > > I have changed the BLOCKSIZE to 16KB and triggered a major
> >> compaction. I
> >> > > will report my results once it is done.
> >> > >
> >> > > - Ramu
> >> > >
> >> > >
> >> > > On Mon, Oct 7, 2013 at 3:21 PM, lars hofhansl <[EMAIL PROTECTED]>
> >> wrote:
> >> > >
> >> > >> First of: 128gb heap per RegionServer. Wow.I'd be interested to
> hear
> >> > your
> >> > >> experience with such a large heap for your RS. It's definitely big
> >> > enough.
> >> > >>
> >> > >>
> >> > >> It's interesting hat 100gb do fit into the aggregate cache (of
> >> 8x32gb),
> >> > >> while 1.8tb do not.
> >> > >> Looks like ~70% of the read request would need to bring in a 64kb
> >> block
> >> > >> in order to read 724 bytes.
> >> > >>
> >> > >> Should that take 100ms? No. Something's still amiss.
> >> > >>
> >> > >> Smaller blocks might help (you'd need to bring in 4, 8, or maybe
> 16k
> >> to
> >> > >> read the small row). You would need to issue a major compaction for
> >> > that to
> >> > >> take effect.
> >> > >> Maybe try 16k blocks. If that speeds up your random gets we know
> >> where
> >> > to
> >> > >> look next... At the disk IO.
> >> > >>
> >> > >>
> >> > >> -- Lars
> >> > >>
> >> > >>
> >> > >>
> >> > >> ________________________________
> >> > >>  From: Ramu M S <[EMAIL PROTECTED]>
> >> > >> To: [EMAIL PROTECTED]; lars hofhansl <[EMAIL PROTECTED]>
> >> > >> Sent: Sunday, October 6, 2013 11:05 PM
> >> > >> Subject: Re: HBase Random Read latency > 100ms