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.ma...@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.ma...@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 <la...@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.ma...@gmail.com> > >> To: user@hbase.apache.org; lars hofhansl <la...@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.ma...@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.ma...@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 <la...@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.ma...@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>
