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From Pierre-Luc Brunet <>
Subject Best way to determine how a Cassandra cluster is doing
Date Fri, 23 Dec 2011 23:34:27 GMT
I just imported a lot of data in a 9 node Cassandra cluster and before I create a new ColumnFamily
with even more data, I'd like to be able to determine how full my cluster currently is (in
terms of memory usage). I'm not too sure what I need to look at. I don't want to import another
20-30GB of data and realize I should have added 5-6 more nodes.

In short, I have no idea if I have too few/many nodes right now for what's in the cluster.

Any help would be greatly appreciated :)

$ nodetool -h ring
Address         DC          Rack        Status State   Load            Owns    Token     
                                                                               151236607520417094872610936636341427313    datacenter1 rack1       Up     Normal  7.19 GB         11.11%  0         
                            datacenter1 rack1       Up     Normal  7.18 GB         11.11%  18904575940052136859076367079542678414    datacenter1 rack1       Up     Normal  7.23 GB         11.11%  37809151880104273718152734159085356828    datacenter1 rack1       Up     Normal  4.2 GB          11.11%  56713727820156410577229101238628035242    datacenter1 rack1       Up     Normal  4.25 GB         11.11%  75618303760208547436305468318170713656    datacenter1 rack1       Up     Normal  4.1 GB          11.11%  94522879700260684295381835397713392071    datacenter1 rack1       Up     Normal  4.83 GB         11.11%  113427455640312821154458202477256070485    datacenter1 rack1       Up     Normal  2.24 GB         11.11%  132332031580364958013534569556798748899    datacenter1 rack1       Up     Normal  3.06 GB         11.11%  151236607520417094872610936636341427313

# nodetool -h cfstats
  Keyspace: stats
  Read Count: 232
  Read Latency: 39.191931034482764 ms.
  Write Count: 160678758
  Write Latency: 0.0492021849459404 ms.
  Pending Tasks: 0
    Column Family: DailyStats
    SSTable count: 5267
    Space used (live): 7710048931
    Space used (total): 7710048931
    Number of Keys (estimate): 10701952
    Memtable Columns Count: 4401
    Memtable Data Size: 23384563
    Memtable Switch Count: 14368
    Read Count: 232
    Read Latency: 29.047 ms.
    Write Count: 160678813
    Write Latency: 0.053 ms.
    Pending Tasks: 0
    Bloom Filter False Postives: 0
    Bloom Filter False Ratio: 0.00000
    Bloom Filter Space Used: 115533264
    Key cache capacity: 200000
    Key cache size: 1894
    Key cache hit rate: 0.627906976744186
    Row cache: disabled
    Compacted row minimum size: 216
    Compacted row maximum size: 42510
    Compacted row mean size: 3453

[default@stats] describe;
Keyspace: stats:
  Replication Strategy: org.apache.cassandra.locator.SimpleStrategy
  Durable Writes: true
    Options: [replication_factor:3]
  Column Families:
    ColumnFamily: DailyStats (Super)
      Key Validation Class: org.apache.cassandra.db.marshal.BytesType
      Default column value validator: org.apache.cassandra.db.marshal.UTF8Type
      Columns sorted by: org.apache.cassandra.db.marshal.UTF8Type/org.apache.cassandra.db.marshal.UTF8Type
      Row cache size / save period in seconds / keys to save : 0.0/0/all
      Row Cache Provider: org.apache.cassandra.cache.ConcurrentLinkedHashCacheProvider
      Key cache size / save period in seconds: 200000.0/14400
      GC grace seconds: 864000
      Compaction min/max thresholds: 4/32
      Read repair chance: 1.0
      Replicate on write: true
      Built indexes: []
      Column Metadata:
      Compaction Strategy: org.apache.cassandra.db.compaction.LeveledCompactionStrategy
      Compression Options:

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