incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Romain HARDOUIN <romain.hardo...@urssaf.fr>
Subject Why so many SSTables?
Date Tue, 10 Apr 2012 14:24:01 GMT
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
Mime
View raw message