On 13.09.2017 19:03, James Okken wrote:
Hi,
Novice question here:
The way I understand CEPH is that it distributes data in OSDs in a
cluster. The reads and writes come across the ethernet as RBD requests
and the actual data IO then also goes across the ethernet.
I have a CEPH environment being setup on a fiber channel disk array
(via an openstack fuel deploy). The servers using the CEPH storage
also have access to the same fiber channel disk array.
From what I understand those servers would need to make the RDB
requests and do the IO across ethernet, is that correct? Even though
with this infrastructure setup there is a “shorter” and faster path to
those disks, via the fiber channel.
Is there a way to access storage on a CEPH cluster when one has this
“better” access to the disks in the cluster? (how about if it were to
be only a single OSD with replication set to 1)
Sorry if this question is crazy…
thanks
a bit cracy :)
if the disks are directly attached on a OSD node, or attachable on
Fiberchannel does not make a difference. you can not shortcut the ceph
cluster and talk to the osd disks directly without eventually destroying
the ceph cluster.
Even if you did, ceph is an object storage on disk, so you would not
find filesystem or RBD diskimages there, only objects on your FC
attached osd node disks with filestore, and with bluestore not even
readable objects.
that beeing said I think a FC SAN attached ceph osd node sounds a bit
strange. ceph's strength is the distributed scaleable solution. and
having the osd nodes collected on a SAN array would nuter ceph's
strengths, and amplify ceph's weakness of high latency. i would only
consider such a solution for testing, learning or playing around without
having actual hardware for a distributed system. and in that case use 1
lun for each osd disk, give 8-10 vm's some luns/osd's each, just to
learn how to work with ceph.
if you want to have FC SAN attached storage on servers, shareable
between servers in a usable fashion I would rather mount the same SAN
lun on multiple servers and use a cluster filesystem like ocfs or gfs
that is made for this kind of solution.
kind regards
Ronny Aasen
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