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From Erik Forkalsrud <>
Subject Re: FW: Very slow batch insert using version 0.7.2
Date Fri, 11 Mar 2011 20:02:24 GMT
On 03/11/2011 04:56 AM, Zhu Han wrote:
>     When I run it on my laptop (Fedora 14, 64-bit, 4 cores, 8GB RAM)
>      it flushes one Memtable with 5000 operations
>     When I run it on a server  (RHEL5, 64-bit, 16 cores, 96GB RAM) it
>     flushes 100 Memtables with anywhere between 1 operation and 359
>     operations (35 bytes and 12499 bytes)
> What's the settings of commit log flush, periodic or in batch?

It's whatever the default setting is, (in the cassandra.yaml that is 
packaged in the apache-cassandra-0.7.3-bin.tar.gz download) specifically:

    commitlog_rotation_threshold_in_mb: 128
    commitlog_sync: periodic
    commitlog_sync_period_in_ms: 10000
    flush_largest_memtables_at: 0.75

If I describe keyspace I get:

    [default@unknown] describe keyspace Events;
    Keyspace: Events:
      Replication Strategy: org.apache.cassandra.locator.SimpleStrategy
        Replication Factor: 1
      Column Families:
        ColumnFamily: Event
          Columns sorted by: org.apache.cassandra.db.marshal.TimeUUIDType
          Row cache size / save period: 0.0/0
          Key cache size / save period: 200000.0/14400
          Memtable thresholds: 14.109375/3010/1440
          GC grace seconds: 864000
          Compaction min/max thresholds: 4/32
          Read repair chance: 1.0
          Built indexes: []

It turns out my suspicion was right. When I tried overriding the jvm 
memory parameters calculated in conf/ to use the values 
calculated on my 8GB laptop like this:

    MAX_HEAP_SIZE=3932m HEAP_NEWSIZE=400m ./

That made the server behave much nicer.  This time it kept all 5000 
operations in a single Memtable.  Also, when running with these memory 
settings the Memtable thresholds changed to "1.1390625/243/1440"   (from 
"14.109375/3010/1440")      (all the other output from "describe 
keyspace" remains the same)

So it looks like something goes wrong when cassandra gets too much memory.

Erik Forkalsrud
Commission Junstion

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