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From Richard Low <rich...@wentnet.com>
Subject Re: Cassandra and RAIDs
Date Wed, 24 Jul 2013 15:15:33 GMT
On 24 July 2013 15:36, Jan Algermissen <jan.algermissen@nordsc.com> wrote:


> 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?
>

It's not necessary, due to replication as you say.  You can give Cassandra
your JBOD disks and it will split data between them and avoid a disk (or
fail the node, you can choose) if one fails.

There are some reasons to consider RAID though:

* It is probably quicker and places no load on the rest of the cluster to
do a RAID rebuild rather than a nodetool rebuild/repaid.  The importance of
this depends on how much data you have and the load on your cluster.  If
you don't have much data per node or if there is spare capacity then RAID
will offer no benefit here.
* Using JBOD, the largest SSTable you can have is limited to the size of
one disk.  This is unlikely to cause problems in most scenarios but an
erroneous nodetool compact could cause problems if your data size is
greater than can fit on any one disk.

Richard.

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