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From Apache Wiki <>
Subject [Cassandra Wiki] Update of "StorageConfiguration" by tuxracer69
Date Sun, 15 Nov 2009 10:08:41 GMT
Dear Wiki user,

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The "StorageConfiguration" page has been changed by tuxracer69.


- Cassandra storage configuration is described by the conf/storage-conf.xml file.
+ Cassandra storage configuration is described by the ''conf/storage-conf.xml'' file. As the
syntax evolves with releases, this wiki page tries to document those changes using ''[New
in X.Y: ....]'' lines.
+ == AutoBootstrap ==
+ ''[New in 0.5:''
+ Turn on to make new [non-seed] nodes automatically migrate the right data 
+ to themselves.  (If no InitialToken is specified, they will pick one 
+ such that they will get half the range of the most-loaded node.)
+ If a node starts up without bootstrapping, it will mark itself bootstrapped
+ so that you can't subsequently accidently bootstrap a node with
+ data on it.  (You can reset this by wiping your data and commitlog
+ directories.)
+ Off by default so that new clusters and upgraders from 0.4 don't
+ bootstrap immediately.  You should turn this on when you start adding
+ new nodes to a cluster that already has data on it.  (If you are upgrading
+ from 0.4, start your cluster with it off once before changing it to true.
+ Otherwise, no data will be lost but you will incur a lot of unnecessary
+ I/O before your cluster starts up.)
+ {{{
+   <AutoBootstrap>false</AutoBootstrap>
+ }}}
+ '']''
  == Cluster Name ==
  The name of this cluster.  This is mainly used to prevent machines in one logical cluster
from joining another.
@@ -20, +42 @@

   <Keyspace Name="Keyspace1">
+ ''[New in 0.5:''
+ The fraction of keys per sstable whose locations we keep in
+ memory in "mostly LRU" order.  (JUST the key locations, NOT any
+ column values.)
+ The amount of memory used by the default setting of 0.01 is
+ comparable to the amount used by the internal per-sstable key
+ index. Consider increasing this if you have fewer, wider rows.
+ Set to 0 to disable entirely.
+ {{{
+       <KeysCachedFraction>0.01</KeysCachedFraction>
+ }}}
+ '']''
  The {{{CompareWith}}} attribute tells Cassandra how to sort the columns for slicing operations.
 The default is {{{BytesType}}}, which is a straightforward lexical comparison of the bytes
in each column. Other options are {{{AsciiType}}}, {{{UTF8Type}}}, {{{LexicalUUIDType}}},
{{{TimeUUIDType}}}, and {{{LongType}}}.  You can also specify the fully-qualified class name
to a class of your choice extending {{{org.apache.cassandra.db.marshal.AbstractType}}}.
@@ -34, +70 @@

  (To get the closest approximation to 0.3-style {{{supercolumns}}}, you would use {{{CompareWith=UTF8Type
  If {{{FlushPeriodInMinutes}}} is configured and positive, it will be flushed to disk with
that period whether it is dirty or not.  This is intended for lightly-used {{{columnfamilies}}}
so that they do not prevent commitlog segments from being purged.
+ ''[New in 0.5:''
+ An optional `Comment` attribute may be used to attach additional human-readable information
about the column family to its definition.
+ '']''
  <ColumnFamily CompareWith="BytesType"
@@ -46, +86 @@

  <ColumnFamily ColumnType="Super"
-        Name="Super1"/>
+        Name="Super1"
+        Comment="A column family with supercolumns, whose column and subcolumn names are
UTF8 strings"/>
  == Partitioner ==
@@ -98, +139 @@

  <CalloutLocation>/var/lib/cassandra/callouts</CalloutLocation> <BootstrapFileDirectory>/var/lib/cassandra/bootstrap</BootstrapFileDirectory>
+ ''[New in 0.5:''
+ {{{
+   <BootstrapFileDirectory>/var/lib/cassandra/bootstrap</BootstrapFileDirectory>
+ }}}
+ '']''
  == Hosts ==
  Addresses of hosts that are deemed contact points. Cassandra nodes use this list of hosts
to find each other and learn the topology of the ring. You must change this if you are running
multiple nodes!

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