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From Apache Wiki <wikidi...@apache.org>
Subject [Cassandra Wiki] Update of "StorageConfiguration" by JonHermes
Date Wed, 27 Oct 2010 22:21:58 GMT
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 JonHermes.
http://wiki.apache.org/cassandra/StorageConfiguration?action=diff&rev1=48&rev2=49

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

  
   * '''dynamic_snitch''' and '''endpoint_snitch'''
  
+ !EndPointSnitch: Setting this to the class that implements {{{IEndPointSnitch}}} which will
see if two endpoints are in the same data center or on the same rack. Out of the box, Cassandra
provides {{{org.apache.cassandra.locator.RackInferringSnitch}}} which will assume that the
2nd and 3rd octets of the IP contain the datacenter and rack, {{{org.apache.cassandra.locator.SimpleSnitch}}}
which will do nothing, {{{org.apache.cassandra.locator.PropertyFileSnitch}}} which will read
from cassandra-topology.properties to give explicit proximities, and {{{org.apache.cassandra.locator.EC2Snitch}}}
which will read the region and zone from the ec2 node and use them as datacenter and rack.
- !EndPointSnitch: Setting this to the class that implements {{{IEndPointSnitch}}} which will
see if two endpoints are in the same data center or on the same rack. Out of the box, Cassandra
provides {{{org.apache.cassandra.locator.RackInferringSnitch}}}
- 
- Note: this class will work on hosts' IPs only. There is no configuration parameter to tell
Cassandra that a node is in rack ''R'' and in datacenter ''D''. The current rules are based
on the two methods:
- 
-  a. isOnSameRack: Look at the IP Address of the two hosts. Compare the 3rd octet. If they
are the same then the hosts are in the same rack else different racks.
- 
-  a. isInSameDataCenter: Look at the IP Address of the two hosts. Compare the 2nd octet.
If they are the same then the hosts are in the same datacenter else different datacenter.
  
  Dynamic Snitch is a boolean that controls if the above snitch is wrapped with a dynamic
snitch, which will monitor read latencies and avoid reading from hosts that have slowed.
  

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