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 >> > >> >> > >> >> > >> 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 <[email protected]> >> 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 <[email protected]> >> > 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 <[email protected]> >> > >> 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 <[email protected]> >> > >> >>> To: [email protected] >> > >> >>> 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> >> > >
