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From Jean-Marc Spaggiari <jean-m...@spaggiari.org>
Subject Re: HBase Random Read latency > 100ms
Date Mon, 07 Oct 2013 11:45:31 GMT
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 <ramu.malur@gmail.com>

> 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 <ramu.malur@gmail.com> 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 <
> > bharathv@cloudera.com> 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 <ramu.malur@gmail.com> 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 <ramu.malur@gmail.com>
> 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 <larsh@apache.org>
> >> 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 <ramu.malur@gmail.com>
> >> > >> To: user@hbase.apache.org; lars hofhansl <larsh@apache.org>
> >> > >> Sent: Sunday, October 6, 2013 11:05 PM
> >> > >> Subject: Re: HBase Random Read latency > 100ms
> >> > >>
> >> > >>
> >> > >> Lars,
> >> > >>
> >> > >> In one of your old posts, you had mentioned that lowering the
> >> BLOCKSIZE
> >> > is
> >> > >> good for random reads (of course with increased size for Block
> >> Indexes).
> >> > >>
> >> > >> Post is at
> >> > http://grokbase.com/t/hbase/user/11bat80x7m/row-get-very-slow
> >> > >>
> >> > >> Will that help in my tests? Should I give it a try? If I alter
my
> >> table,
> >> > >> should I trigger a major compaction again for this to take effect?
> >> > >>
> >> > >> Thanks,
> >> > >> Ramu
> >> > >>
> >> > >>
> >> > >>
> >> > >> On Mon, Oct 7, 2013 at 2:44 PM, Ramu M S <ramu.malur@gmail.com>
> >> wrote:
> >> > >>
> >> > >> > Sorry BLOCKSIZE was wrong in my earlier post, it is the default
> 64
> >> KB.
> >> > >> >
> >> > >> > {NAME => 'usertable', FAMILIES => [{NAME => 'cf',
> >> DATA_BLOCK_ENCODING
> >> > =>
> >> > >> > 'NONE', BLOOMFILTER => 'ROWCOL', REPLICATION_SCOPE =>
'0',
> >> VERSIONS =>
> >> > >> '1',
> >> > >> > COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL =>
'2147483647',
> >> > >> > KEEP_DELETED_CELLS => 'false', BLOCKSIZE => '65536',
IN_MEMORY =>
> >> > >> 'false',
> >> > >> > ENCODE_ON_DISK => 'true', BLOCKCACHE => 'true'}]}
> >> > >> >
> >> > >> > Thanks,
> >> > >> > Ramu
> >> > >> >
> >> > >> >
> >> > >> > On Mon, Oct 7, 2013 at 2:42 PM, Ramu M S <ramu.malur@gmail.com>
> >> > wrote:
> >> > >> >
> >> > >> >> Lars,
> >> > >> >>
> >> > >> >> - Yes Short Circuit reading is enabled on both HDFS and
HBase.
> >> > >> >> - I had issued Major compaction after table is loaded.
> >> > >> >> - Region Servers have max heap set as 128 GB. Block Cache
Size
> is
> >> > 0.25
> >> > >> of
> >> > >> >> heap (So 32 GB for each Region Server) Do we need even
more?
> >> > >> >> - Decreasing HFile Size (Default is 1GB )? Should I leave
it to
> >> > >> default?
> >> > >> >> - Keys are Zipfian distributed (By YCSB)
> >> > >> >>
> >> > >> >> Bharath,
> >> > >> >>
> >> > >> >> Bloom Filters are enabled. Here is my table details,
> >> > >> >> {NAME => 'usertable', FAMILIES => [{NAME =>
'cf',
> >> DATA_BLOCK_ENCODING
> >> > >> =>
> >> > >> >> 'NONE', BLOOMFILTER => 'ROWCOL', REPLICATION_SCOPE
=> '0',
> >> VERSIONS
> >> > =>
> >> > >> '1',
> >> > >> >> COMPRESSION => 'NONE', MIN_VERSIONS => '0', TTL
=> '2147483647
> ',
> >> > >> >> KEEP_DELETED_CELLS => 'false', BLOCKSIZE => '16384',
IN_MEMORY
> =>
> >> > >> 'false',
> >> > >> >> ENCODE_ON_DISK => 'true', BLOCKCACHE => 'true'}]}
> >> > >> >>
> >> > >> >> When the data size is around 100GB (100 Million records),
then
> the
> >> > >> >> latency is very good. I am getting a throughput of around
300K
> >> OPS.
> >> > >> >> In both cases (100 GB and 1.8 TB) Ganglia stats show
that Disk
> >> reads
> >> > >> are
> >> > >> >> around 50-60 MB/s throughout the read cycle.
> >> > >> >>
> >> > >> >> Thanks,
> >> > >> >> Ramu
> >> > >> >>
> >> > >> >>
> >> > >> >> On Mon, Oct 7, 2013 at 2:21 PM, lars hofhansl <larsh@apache.org
> >
> >> > >> wrote:
> >> > >> >>
> >> > >> >>> Have you enabled short circuit reading? See here:
> >> > >> >>> http://hbase.apache.org/book/perf.hdfs.html
> >> > >> >>>
> >> > >> >>> How's your data locality (shown on the RegionServer
UI page).
> >> > >> >>>
> >> > >> >>>
> >> > >> >>> How much memory are you giving your RegionServers?
> >> > >> >>> If you reads are truly random and the data set does
not fit
> into
> >> the
> >> > >> >>> aggregate cache, you'll be dominated by the disk
and network.
> >> > >> >>> Each read would need to bring in a 64k (default)
HFile block.
> If
> >> > short
> >> > >> >>> circuit reading is not enabled you'll get two or
three context
> >> > >> switches.
> >> > >> >>>
> >> > >> >>> So I would try:
> >> > >> >>> 1. Enable short circuit reading
> >> > >> >>> 2. Increase the block cache size per RegionServer
> >> > >> >>> 3. Decrease the HFile block size
> >> > >> >>> 4. Make sure your data is local (if it is not, issue
a major
> >> > >> compaction).
> >> > >> >>>
> >> > >> >>>
> >> > >> >>> -- Lars
> >> > >> >>>
> >> > >> >>>
> >> > >> >>>
> >> > >> >>> ________________________________
> >> > >> >>>  From: Ramu M S <ramu.malur@gmail.com>
> >> > >> >>> To: user@hbase.apache.org
> >> > >> >>> Sent: Sunday, October 6, 2013 10:01 PM
> >> > >> >>> Subject: HBase Random Read latency > 100ms
> >> > >> >>>
> >> > >> >>>
> >> > >> >>> 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,
> >> > >> >>> hdfs-site.xml)
> >> > >> >>>
> >> > >> >>> <property>
> >> > >> >>>   <name>hbase.ipc.client.tcpnodelay</name>
> >> > >> >>>   <value>true</value>
> >> > >> >>> </property>
> >> > >> >>>
> >> > >> >>> <property>
> >> > >> >>>   <name>ipc.server.tcpnodelay</name>
> >> > >> >>>   <value>true</value>
> >> > >> >>> </property>
> >> > >> >>>
> >> > >> >>> 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?
> >> > >> >>>
> >> > >> >>> Thanks,
> >> > >> >>> Ramu
> >> > >> >>>
> >> > >> >>
> >> > >> >>
> >> > >> >
> >> > >>
> >> > >
> >> > >
> >> >
> >>
> >>
> >>
> >> --
> >> Bharath Vissapragada
> >> <http://www.cloudera.com>
> >>
> >
> >
>

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