In general I would limit the data load per node to 300 to 400GB. Otherwise things can painful when it comes time to run compaction / repair / move .
Cheers ----------------- Aaron Morton Freelance Developer @aaronmorton http://www.thelastpickle.com On 12/04/2012, at 1:00 AM, Dave Brosius wrote: > It's easy to spend other people's money, but handling 1TB of data with 1.5 g > heap? Memory is cheap, and just a little more will solve many problems. > > > On 04/11/2012 08:43 AM, Romain HARDOUIN wrote: >> >> >> Thank you for your answers. >> >> I originally post this question because we encoutered an OOM Exception on 2 >> nodes during repair session. >> Memory analyzing shows an hotspot: an ArrayList of SSTableBoundedScanner >> which contains as many objects there are SSTables on disk (7747 objects at >> the time). >> This ArrayList consumes 47% of the heap space (786 MB). >> >> We want each node to handle 1 TB, so we must dramatically reduce the number >> of SSTables. >> >> Thus, is there any drawback if we set sstable_size_in_mb to 200MB? >> Otherwise shoudl we go back to Tiered Compaction? >> >> Regards, >> >> Romain >> >> >> Maki Watanabe <watanabe.m...@gmail.com> a écrit sur 11/04/2012 04:21:47 : >> >> > You can configure sstable size by sstable_size_in_mb parameter for LCS. >> > The default value is 5MB. >> > You should better to check you don't have many pending compaction tasks >> > with nodetool tpstats and compactionstats also. >> > If you have enough IO throughput, you can increase >> > compaction_throughput_mb_per_sec >> > in cassandra.yaml to reduce pending compactions. >> > >> > maki >> > >> > 2012/4/10 Romain HARDOUIN <romain.hardo...@urssaf.fr>: >> > > >> > > Hi, >> > > >> > > We are surprised by the number of files generated by Cassandra. >> > > Our cluster consists of 9 nodes and each node handles about 35 GB. >> > > We're using Cassandra 1.0.6 with LeveledCompactionStrategy. >> > > We have 30 CF. >> > > >> > > We've got roughly 45,000 files under the keyspace directory on each node: >> > > ls -l /var/lib/cassandra/data/OurKeyspace/ | wc -l >> > > 44372 >> > > >> > > The biggest CF is spread over 38,000 files: >> > > ls -l Documents* | wc -l >> > > 37870 >> > > >> > > ls -l Documents*-Data.db | wc -l >> > > 7586 >> > > >> > > Many SSTable are about 4 MB: >> > > >> > > 19 MB -> 1 SSTable >> > > 12 MB -> 2 SSTables >> > > 11 MB -> 2 SSTables >> > > 9.2 MB -> 1 SSTable >> > > 7.0 MB to 7.9 MB -> 6 SSTables >> > > 6.0 MB to 6.4 MB -> 6 SSTables >> > > 5.0 MB to 5.4 MB -> 4 SSTables >> > > 4.0 MB to 4.7 MB -> 7139 SSTables >> > > 3.0 MB to 3.9 MB -> 258 SSTables >> > > 2.0 MB to 2.9 MB -> 35 SSTables >> > > 1.0 MB to 1.9 MB -> 13 SSTables >> > > 87 KB to 994 KB -> 87 SSTables >> > > 0 KB -> 32 SSTables >> > > >> > > FYI here is CF information: >> > > >> > > ColumnFamily: Documents >> > > Key Validation Class: org.apache.cassandra.db.marshal.BytesType >> > > Default column value validator: >> > > org.apache.cassandra.db.marshal.BytesType >> > > Columns sorted by: org.apache.cassandra.db.marshal.BytesType >> > > Row cache size / save period in seconds / keys to save : 0.0/0/all >> > > Row Cache Provider: org.apache.cassandra.cache.SerializingCacheProvider >> > > Key cache size / save period in seconds: 200000.0/14400 >> > > GC grace seconds: 1728000 >> > > Compaction min/max thresholds: 4/32 >> > > Read repair chance: 1.0 >> > > Replicate on write: true >> > > Column Metadata: >> > > Column Name: refUUID (72656655554944) >> > > Validation Class: org.apache.cassandra.db.marshal.BytesType >> > > Index Name: refUUID_idx >> > > Index Type: KEYS >> > > Compaction Strategy: >> > > org.apache.cassandra.db.compaction.LeveledCompactionStrategy >> > > Compression Options: >> > > sstable_compression: >> > > org.apache.cassandra.io.compress.SnappyCompressor >> > > >> > > Is it a bug? If not, how can we tune Cassandra to avoid this? >> > > >> > > Regards, >> > > >> > > Romain >
