Re: how to mount a specific pool in cephs

[Grant Ashman <grant.ashman@mach.com.au>]

Tommi Virtanen <tommi.virtanen <at> dreamhost.com> writes:
> 
> You don't mount pools directly; there's filesystem metadata (as
> managed by metadata servers) that is needed too.
> 
> What you probably want is to specify that a subtree of your ceph dfs
> stores the file data in a separate pool, using "cephfs
> /mnt/ceph/some/subtree set_layout --pool 6". Note that a numerical
> pool id is currently required.
> 
> http://ceph.newdream.net/docs/master/man/8/cephfs/
> 
> You can mount any subtree of the ceph dfs directly, using
> 10.32.0.10:6789:/some/subtree in your mount command.
> 

Hi Tommi,

We have tried setting the layout as described below with:
'cephfs /mnt/ceph-backup/ set_layout --pool 3'

However, I only ever receive the following output;
'Error setting layout: Invalid argument'

I can run other view the current layout of the mount 
point, but cannot change the pool layout.

My understanding of the numeric pool is as follows:

root@dsan-test:/mnt# ceph osd dump -o -|grep 'pool'
pool 0 'data' rep size 2 crush_ruleset 0
pool 1 'metadata' rep size 2 crush_ruleset 1
pool 2 'rbd' rep size 2 crush_ruleset 2
pool 3 'backup' rep size 2 crush_ruleset 0 

(omitted detail I thought unnecessary)

Therefore the backup pool which we specifically want to mount is 3?

Are you able to assist with the syntax for cephfs set_layout?

Thanks
Grant