You can use multiple "steps" in your crush map in order to do things
like choose two different hosts then choose a further OSD on one of the
hosts and do another replication so that you can get three replicas onto
two hosts without risking ending up with three replicas on a single node.
On 28/07/2014 18:14, Craig Lewis wrote:
That's expected. You need > 50% of the monitors up. If you only have
2 machines, rebooting one means that 50% are up, so the cluster halts
operations. That's done on purpose to avoid problems when the cluster
is divided in exactly half, and both halves continue to run thinking
the other half is down. Monitors don't need a lot of resources. I'd
recommend that you add a small box as a third monitor. A VM is fine,
as long as it has enough IOPS to it's disks.
It's best to have 3 storage nodes. A new, out of the box install
tries to store data on at least 3 separate hosts. You can lower the
replication level to 2, or change the rules so that it will store data
on 3 separate disks. It might store all 3 copies on the same host
though, so lowering the replication level to 2 is probably better.
I think it's possible to require data stored on 3 disks, with 2 of the
disks coming from different nodes. Editing the CRUSH rules is a bit
advanced: http://ceph.com/docs/master/rados/operations/crush-map/
On Mon, Jul 28, 2014 at 9:59 AM, Don Pinkster <d...@pinkster.me
<mailto:d...@pinkster.me>> wrote:
Hi,
Currently I am evalutating multiple distributed storage solutions
with an S3-like interface.
We have two huge machines with big amounts of storage. Is it
possible to let these two behave exactly the same with Ceph? My
idea is runninng both MON and OSD on these two machines.
With quick tests the cluster is degrated after a reboot of 1 host
and is not able to recover from the reboot.
Thanks in advance!
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