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Date: Mon, 26 Apr 2010 10:27:46 +0200
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Subject: Can Cassandra make real use of several DataFileDirectories?
From: =?ISO-8859-1?Q?Roland_H=E4nel?= <roland@haenel.me>
To: user@cassandra.apache.org
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I have a configuration like this:

  <DataFileDirectories>
      <DataFileDirectory>/storage01/cassandra/data</DataFileDirectory>
      <DataFileDirectory>/storage02/cassandra/data</DataFileDirectory>
      <DataFileDirectory>/storage03/cassandra/data</DataFileDirectory>
  </DataFileDirectories>

After loading a big chunk of data into cassandra, I end up wich some 70GB in
the first directory, and only about 10GB in the second and third one. All
rows are quite small, so it's not just some big rows that contain the
majority of data.

Does Cassandra have the ability to 'see' the maximum available space in
these directory? I'm asking myself this question since my limit is 100GB,
and the first directory is approaching this limit...

And, wouldn't it be better if Cassandra tried to 'load-balance' the files
inside the directories because this will result in better (read) performance
if the directories are on different disks (which is the case for me)?

Any help is appreciated.

Roland

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I have a configuration like this:<br><br>=A0 &lt;DataFileDirectories&gt;<br=
>=A0=A0=A0=A0=A0 &lt;DataFileDirectory&gt;/storage01/cassandra/data&lt;/Dat=
aFileDirectory&gt;<br>=A0=A0=A0=A0=A0 &lt;DataFileDirectory&gt;/storage02/c=
assandra/data&lt;/DataFileDirectory&gt;<br>
=A0=A0=A0=A0=A0 &lt;DataFileDirectory&gt;/storage03/cassandra/data&lt;/Data=
FileDirectory&gt;<br>=A0 &lt;/DataFileDirectories&gt;<br><br>After loading =
a big chunk of data into cassandra, I end up wich some 70GB in the first di=
rectory, and only about 10GB in the second and third one. All rows are quit=
e small, so it&#39;s not just some big rows that contain the majority of da=
ta.<br>
<br>Does Cassandra have the ability to &#39;see&#39; the maximum available =
space in these directory? I&#39;m asking myself this question since my limi=
t is 100GB, and the first directory is approaching this limit...<br><br>
And, wouldn&#39;t it be better if Cassandra tried to &#39;load-balance&#39;=
 the files inside the directories because this will result in better (read)=
 performance if the directories are on different disks (which is the case f=
or me)?<br>
<br>Any help is appreciated.<br><br>Roland<br><br>

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