On 06/12/2014 07:27 AM, Christian Kauhaus wrote:
Am 12.06.2014 14:09, schrieb Loic Dachary:
With the replication factor set to three (which is the default), it can
tolerate that two OSD fail at the same time.
I've noticed that a replication factor of 3 is the new default in firefly.
What rationale led to changing the default? It used to be 2. A replication
factor of 3 incurs significantly more space overhead. Has a replication factor
of 2 been proven to be insecure?
Afaik more customers wanted 3x replication than 2x replication in
production deployments so we changed the default. Having said that, it
all depends on what you want. If you have tape backup, maybe 2x is good
enough for you. Or maybe you want the extra availability and redundancy
3x provides. Heck, if you really want to you can run RAID6 under the
OSDs with no replication like what people typically do with
lustre/gluster. Or use our new erasure coding. Fortunately (or
unfortunately) Ceph gives you a lot of options. :)
Mark
Regards
Christian
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