On 05/08/2013 17:15, Mike Dawson wrote:
Short answer: Ceph generally is used with multiple OSDs per node. One
OSD per storage drive with no RAID is the most common setup. At 24- or
36-drives per chassis, there are several potential bottlenecks to
consider.
Mark Nelson, the Ceph performance guy at Inktank, has published
several articles you should consider reading. A few of interest are
[0], [1], and [2]. The last link is a 5-part series.
Yep, I saw [0] and [1]. He tries a 6-disk RAID0 array and generally gets
lower throughput than 6 x JBOD disks (although I think he's using the
controller RAID0 functionality, rather than mdraid).
AFAICS he has a 36-disk chassis but only runs tests with 6 disks, which
is a shame as it would be nice to know which other bottleneck you could
hit first with this type of setup.
Also, note that there is on-going work to add erasure coding as a
optional backend (as opposed to the current replication scheme). If
you prioritize bulk storage over performance, you may be interested in
following the progress [3], [4], and [5].
[0]:
http://ceph.com/community/ceph-performance-part-1-disk-controller-write-throughput/
[1]:
http://ceph.com/community/ceph-performance-part-2-write-throughput-without-ssd-journals/
[2]:
http://ceph.com/performance-2/ceph-cuttlefish-vs-bobtail-part-1-introduction-and-rados-bench/
[3]:
http://wiki.ceph.com/01Planning/02Blueprints/Dumpling/Erasure_encoding_as_a_storage_backend
[4]:
http://wiki.ceph.com/01Planning/02Blueprints/Dumpling/Erasure_encoding_as_a_storage_backend
[5]: http://www.inktank.com/about-inktank/roadmap/
Thank you - erasure coding is very much of interest for the
archival-type storage I'm looking at. However your links [3] and [4] are
identical, did you mean to link to another one?
Cheers,
Brian.
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