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From Andrew Cobley <a.e.cob...@dundee.ac.uk>
Subject Re: Cassandra and RAIDs
Date Wed, 24 Jul 2013 15:16:17 GMT
From:

http://www.datastax.com/docs/1.2/cluster_architecture/cluster_planning

  *   RAID on data disks: It is generally not necessary to use RAID for the following reasons:

  *   Data is replicated across the cluster based on the replication factor you've chosen.
  *   Starting in version 1.2, Cassandra includes takes care of disk management with the JBOD
(Just a bunch of disks) support feature. Because Cassandra properly reacts to a disk failure,
based on your availability/consistency requirements, either by stopping the affected node
or by blacklisting the failed drive, this allows you to deploy Cassandra nodes with large
disk arrays without the overhead of RAID 10.

  *   RAID on the commit log disk: Generally RAID is not needed for the commit log disk. Replication
adequately prevents data loss. If you need the extra redundancy, use RAID 1.


Andy

On 24 Jul 2013, at 15:36, Jan Algermissen <jan.algermissen@nordsc.com<mailto:jan.algermissen@nordsc.com>>
wrote:

Hi,

second question:

is it recommended to set up Cassandra using 'RAID-ed' disks for per-node reliability or do
people usually just rely on having the multiple nodes anyway - why bother with replicated
disks?

Jan


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