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From: Apache Wiki <wikidiffs@apache.org>
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Date: Fri, 13 Nov 2009 15:41:22 -0000
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Subject: 
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Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Cassandra Wiki" for=
 change notification.

The "StorageConfiguration" page has been changed by tuxracer69.
http://wiki.apache.org/cassandra/StorageConfiguration?action=3Ddiff&rev1=3D=
1&rev2=3D2

--------------------------------------------------

  }}}
  =

  =3D=3D Keyspaces and ColumnFamilies =3D=3D
- Keyspaces and !ColumnFamilies: A !ColumnFamily is the Cassandra concept c=
losest to a relational table.  !Keyspaces are separate groups of !ColumnFam=
ilies.  Except in very unusual circumstances you will have one Keyspace per=
 application.
+ Keyspaces and {{{ColumnFamilies}}}: A {{{ColumnFamily}}} is the Cassandra=
 concept closest to a relational table.  {{{Keyspaces}}} are separate group=
s of {{{ColumnFamilies}}}.  Except in very unusual circumstances you will h=
ave one Keyspace per application.
  =

  There is an implicit keyspace named 'system' for Cassandra internals.
  =

@@ -21, +21 @@

   <Keyspace Name=3D"Keyspace1">
  }}}
  =

- The !CompareWith attribute tells Cassandra how to sort the columns for sl=
icing operations.  The default is !BytesType, which is a straightforward le=
xical comparison of the bytes in each column. Other options are !AsciiType,=
 !UTF8Type, !LexicalUUIDType, !TimeUUIDType, and !LongType.  You can also s=
pecify the fully-qualified class name to a class of your choice extending o=
rg.apache.cassandra.db.marshal.AbstractType.
+ The {{{CompareWith}}} attribute tells Cassandra how to sort the columns f=
or slicing operations.  The default is {{{BytesType}}}, which is a straight=
forward 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.Abstra=
ctType}}}.
  =

- !SuperColumns have a similar !CompareSubcolumnsWith attribute.
+  * {{{SuperColumns}}} have a similar {{{CompareSubcolumnsWith}}} attribut=
e.
+  * {{{BytesType}}}: Simple sort by byte value.  No validation is performe=
d. =

+  * {{{AsciiType}}}: Like {{{BytesType}}}, but validates that the input ca=
n be parsed as US-ASCII.
+  * {{{UTF8Type}}}: A string encoded as UTF8 =

+  * {{{LongType}}}: A 64bit long =

+  * {{{LexicalUUIDType}}}: A 128bit UUID, compared lexically (by byte valu=
e) =

+  * {{{TimeUUIDType}}}: a 128bit version 1 UUID, compared by timestamp
  =

- BytesType: Simple sort by byte value.  No validation is performed. !Ascii=
Type: Like !BytesType, but validates that the input can be parsed as US-ASC=
II.
- =

- UTF8Type: A string encoded as UTF8 !LongType: A 64bit long !LexicalUUIDTy=
pe: A 128bit UUID, compared lexically (by byte value) T!imeUUIDType: a 128b=
it version 1 !UUID, compared by !timestamp
- =

- (To get the closest approximation to 0.3-style !supercolumns, you would u=
se !CompareWith=3DUTF8Type !CompareSubcolumnsWith=3D!LongType.)
+ (To get the closest approximation to 0.3-style {{{supercolumns}}}, you wo=
uld use {{{CompareWith=3DUTF8Type CompareSubcolumnsWith=3DLongType}}}.)
  =

- If !FlushPeriodInMinutes is configured and positive, it will be flushed t=
o disk with that period whether it is dirty or not.  This is intended for l=
ightly-used !columnfamilies so that they do not prevent !commitlog segments=
 from being purged.
+ If {{{FlushPeriodInMinutes}}} is configured and positive, it will be flus=
hed 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.
  =

  {{{
  <ColumnFamily CompareWith=3D"BytesType"
-  Name=3D"Standard1"
+        Name=3D"Standard1"
-   FlushPeriodInMinutes=3D"60"/>
+        FlushPeriodInMinutes=3D"60"/>
-  <ColumnFamily CompareWith=3D"UTF8Type" Name=3D"Standard2"/> <ColumnFamil=
y CompareWith=3D"TimeUUIDType" Name=3D"StandardByUUID1"/> <ColumnFamily Col=
umnType=3D"Super"
- CompareWith=3D"UTF8Type" CompareSubcolumnsWith=3D"UTF8Type" Name=3D"Super=
1"/>
- </Keyspace>
- </Keyspaces>
+ <ColumnFamily CompareWith=3D"UTF8Type" =

+        Name=3D"Standard2"/> =

+ <ColumnFamily CompareWith=3D"TimeUUIDType" =

+        Name=3D"StandardByUUID1"/> =

+ <ColumnFamily ColumnType=3D"Super"
+        CompareWith=3D"UTF8Type" =

+        CompareSubcolumnsWith=3D"UTF8Type" =

+        Name=3D"Super1"/>
  }}}
  =

  =3D=3D Partitioner =3D=3D
- Partitioner: any !IPartitioner may be used, including your own as long as=
 it is on the !classpath.  Out of the box, Cassandra provides org.apache.ca=
ssandra.dht.RandomPartitioner, org.apache.cassandra.dht.OrderPreservingPart=
itioner, and org.apache.cassandra.dht.CollatingOrderPreservingPartitioner. =
(CollatingOPP colates according to EN,US rules, not naive byte ordering.  U=
se this as an example if you need locale-aware collation.) Range queries re=
quire using an order-preserving partitioner.
+ Partitioner: any {{{IPartitioner}}} may be used, including your own as lo=
ng as it is on the classpath.  Out of the box, Cassandra provides {{{org.ap=
ache.cassandra.dht.RandomPartitioner}}}, {{{org.apache.cassandra.dht.OrderP=
reservingPartitioner}}}, and {{{org.apache.cassandra.dht.CollatingOrderPres=
ervingPartitioner}}}. (CollatingOPP colates according to EN,US rules, not n=
aive byte ordering.  Use this as an example if you need locale-aware collat=
ion.) Range queries require using an order-preserving partitioner.
  =

  Achtung!  Changing this parameter requires wiping your data directories, =
since the partitioner can modify the !sstable on-disk format.
  =

@@ -56, +62 @@

  =

  If you are using an order-preserving partitioner and you know your key di=
stribution, you can specify the token for this node to use. (Keys are sent =
to the node with the "closest" token, so distributing your tokens equally a=
long the key distribution space will spread keys evenly across your cluster=
.)  This setting is only checked the first time a node is started.
  =

- This can also be useful with RandomPartitioner to force equal spacing of =
tokens around the hash space, especially for clusters with a small number o=
f nodes.
+ This can also be useful with {{{RandomPartitioner}}} to force equal spaci=
ng of tokens around the hash space, especially for clusters with a small nu=
mber of nodes.
  =

  {{{
  <InitialToken></InitialToken>
  }}}
  =

  =3D=3D EndPointSnitch =3D=3D
- !EndPointSnitch: Setting this to the class that implements !IEndPointSnit=
ch which will see if two endpoints are in the same data center or on the sa=
me rack. Out of the box, Cassandra provides org.apache.cassandra.locator.En=
dPointSnitch
+ !EndPointSnitch: Setting this to the class that implements {{{IEndPointSn=
itch}}} which will see if two endpoints are in the same data center or on t=
he same rack. Out of the box, Cassandra provides {{{org.apache.cassandra.lo=
cator.EndPointSnitch}}}
  =

  {{{
  <EndPointSnitch>org.apache.cassandra.locator.EndPointSnitch</EndPointSnit=
ch>
  }}}
  =

  =3D=3D ReplicaPlacementStrategy =3D=3D
- Strategy: Setting this to the class that implements IReplicaPlacementStra=
tegy will change the way the node picker works. Out of the box, Cassandra p=
rovides org.apache.cassandra.locator.RackUnawareStrategy and org.apache.cas=
sandra.locator.RackAwareStrategy (place one replica in a different datacent=
er, and the others on different racks in the same one.)
+ Strategy: Setting this to the class that implements {{{IReplicaPlacementS=
trategy}}} will change the way the node picker works. Out of the box, Cassa=
ndra provides {{{org.apache.cassandra.locator.RackUnawareStrategy}}} and {{=
{org.apache.cassandra.locator.RackAwareStrategy}}} (place one replica in a =
different datacenter, and the others on different racks in the same one.)
  =

  {{{
  <ReplicaPlacementStrategy>org.apache.cassandra.locator.RackUnawareStrateg=
y</ReplicaPlacementStrategy>
@@ -83, +89 @@

  }}}
  =

  =3D=3D Directories =3D=3D
- Directories: Specify where Cassandra should store different data on disk.=
  Keep the data disks and the CommitLog disks separate for best performance
+ Directories: Specify where Cassandra should store different data on disk.=
  Keep the data disks and the {{{CommitLog}}} disks separate for best perfo=
rmance. See also [[FAQ#what_kind_of_hardware_should_i_use|what kind of hard=
ware should I use?]]
  =

  {{{
- <CommitLogDirectory>/var/lib/cassandra/commitlog</CommitLogDirectory> <Da=
taFileDirectories>
+ <CommitLogDirectory>/var/lib/cassandra/commitlog</CommitLogDirectory> =

+ <DataFileDirectories>
- <DataFileDirectory>/var/lib/cassandra/data</DataFileDirectory>
+       <DataFileDirectory>/var/lib/cassandra/data</DataFileDirectory>
  </DataFileDirectories> =

  <CalloutLocation>/var/lib/cassandra/callouts</CalloutLocation> <Bootstrap=
FileDirectory>/var/lib/cassandra/bootstrap</BootstrapFileDirectory> <Stagin=
gFileDirectory>/var/lib/cassandra/staging</StagingFileDirectory>
  }}}
@@ -118, +125 @@

  =

  Address to bind to and tell other nodes to connect to.  You _must_ change=
 this if you want multiple nodes to be able to communicate!
  =

- Leaving it blank leaves it up to InetAddress.getLocalHost(). This will al=
ways do the Right Thing *if* the node is properly configured (hostname, nam=
e resolution, etc), and the Right Thing is to use the address associated wi=
th the hostname (it might not be).
+ Leaving it blank leaves it up to {{{InetAddress.getLocalHost()}}}. This w=
ill always do the Right Thing *if* the node is properly configured (hostnam=
e, name resolution, etc), and the Right Thing is to use the address associa=
ted with the hostname (it might not be).
  =

  {{{
  <ListenAddress>localhost</ListenAddress> =

@@ -128, +135 @@

  <ControlPort>7001</ControlPort>
  }}}
  =

- The address to bind the Thrift RPC service to. Unlike ListenAddress above=
, you *can* specify 0.0.0.0 here if you want Thrift to listen on all interf=
aces.
+ The address to bind the Thrift RPC service to. Unlike {{{ListenAddress}}}=
 above, you *can* specify {{{0.0.0.0}}} here if you want Thrift to listen o=
n all interfaces.
  =

- Leaving this blank has the same effect it does for ListenAddress, (i.e. i=
t will be based on the configured hostname of the node).
+ Leaving this blank has the same effect it does for {{{ListenAddress}}}, (=
i.e. it will be based on the configured hostname of the node).
  =

  {{{
  <ThriftAddress>localhost</ThriftAddress> =

@@ -164, +171 @@

  <ColumnIndexSizeInKB>64</ColumnIndexSizeInKB>
  }}}
  =

- The maximum amount of data to store in memory per !ColumnFamily before fl=
ushing to disk.  Note: There is one memtable per column family, and  this t=
hreshold is based solely on the amount of data stored, not actual heap memo=
ry usage (there is some overhead in indexing the columns).
+ The maximum amount of data to store in memory per !ColumnFamily before fl=
ushing to disk.  Note: There is one memtable per column family, and  this t=
hreshold is based solely on the amount of data stored, not actual heap memo=
ry usage (there is some overhead in indexing the columns). See also [[Memta=
bleThresholds|MemtableThresholds]].
  =

  {{{
  <MemtableSizeInMB>64</MemtableSizeInMB>
- }}
+ }}}
  =

- The maximum number of columns in millions to store in memory per ColumnFa=
mily before flushing to disk.  This is also a per-memtable setting.  Use wi=
th MemtableSizeInMB to tune memory usage.
+ The maximum number of columns in millions to store in memory per ColumnFa=
mily before flushing to disk.  This is also a per-memtable setting.  Use wi=
th {{{MemtableSizeInMB}}} to tune memory usage.
  =

  {{{
  <MemtableObjectCountInMillions>0.1</MemtableObjectCountInMillions>
  }}}
+ =

  Unlike most systems, in Cassandra writes are faster than reads, so you ca=
n afford more of those in parallel.  A good rule of thumb is 2 concurrent r=
eads per processor core.  Increase ConcurrentWrites to the number of client=
s writing at once if you enable CommitLogSync + CommitLogSyncDelay.
  =

  {{{
@@ -183, +191 @@

  =

  !CommitLogSync may be either "periodic" or "batch."  When in batch mode, =
Cassandra won't ack writes until the commit log has been !fsynced to disk. =
 It will wait up to !CommitLogSyncBatchWindowInMS milliseconds for other wr=
ites, before performing the sync.
  =

- This is less necessary in Cassandra than in traditional databases since r=
eplication reduces the odds of losing data from a failure after writing the=
 log entry but before it actually reaches the disk. So the other option is =
"timed," where writes may be acked immediately and the CommitLog is simply =
synced every CommitLogSyncPeriodInMS milliseconds.
+ This is less necessary in Cassandra than in traditional databases since r=
eplication reduces the odds of losing data from a failure after writing the=
 log entry but before it actually reaches the disk. So the other option is =
"timed," where writes may be acked immediately and the CommitLog is simply =
synced every {{{CommitLogSyncPeriodInMS}}} milliseconds.
  =

  {{{
  <CommitLogSync>periodic</CommitLogSync>
@@ -203, +211 @@

  {{{
  <GCGraceSeconds>864000</GCGraceSeconds>
  }}}
- Number of threads to run when flushing memtables to disk.  Set this to th=
e number of disks you physically have in your machine allocated for DataDir=
ectory * 2.  If you are planning to use the Binary Memtable, its recommende=
d to increase the max threads to maintain a higher quality of service while=
 under load when normal memtables are flushing to disk.
+ Number of threads to run when flushing memtables to disk.  Set this to th=
e number of disks you physically have in your machine allocated for {{{Data=
Directory * 2}}}.  If you are planning to use the Binary Memtable, its reco=
mmended to increase the max threads to maintain a higher quality of service=
 while under load when normal memtables are flushing to disk.
  =

  {{{
  <FlushMinThreads>1</FlushMinThreads> <FlushMaxThreads>1</FlushMaxThreads>