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From Apache Wiki <>
Subject [Cassandra Wiki] Update of "MemtableThresholds" by EricEvans
Date Wed, 13 May 2009 20:48:58 GMT
Dear Wiki user,

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The following page has been changed by EricEvans:

New page:
= Memtable Thresholds =

When performing write operations, Cassandra stores values to column-family
specific, in-memory data structures, called Memtables. Memtables
are flused to disk whenever a threshold is exceeded, so it's important to
have these thresholds configured properly configured to keep Memtable size
in check, and memory usage in general with limits.

== MemtableSizeInMB ==

== MemtableObjectCountInMillions ==

== Using Jconsole To Optimize Thresholds ==
Cassandra's column-family mbeans have a number of attributes that can
prove invaluable in determining optimal thresholds. Once way to access
this instrumentation is using Jconsole, a graphical monitoring and
management application that ships with your JDK.

Launching Jconsole with no arguments will display the "New Connection"
dialog box. If you are running Jconsole on the same machine that 
Cassandra is running on, then you can connect using the PID, otherwise
you will need to connect remotely (the default startup scripts for
Cassandra cause the VM to listen on port 8080).


Once connected, select the ''MBeans'' tab, expand the ''org.apache.cassandra.db''
section, and finally one of your column families.

The interesting attributes here are:

 * ''!MemtableColumnsCount:''
 * ''!MemtableDataSize:''
 * ''!MemtableSwitchCount:''



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