On 03/25/2015 05:44 PM, Gregory Farnum wrote:
On Wed, Mar 25, 2015 at 10:36 AM, Jake Grimmett <j...@mrc-lmb.cam.ac.uk> wrote:
Dear All,
Please forgive this post if it's naive, I'm trying to familiarise myself
with cephfs!
I'm using Scientific Linux 6.6. with Ceph 0.87.1
My first steps with cephfs using a replicated pool worked OK.
Now trying now to test cephfs via a replicated caching tier on top of an
erasure pool. I've created an erasure pool, cannot put it under the existing
replicated pool.
My thoughts were to delete the existing cephfs, and start again, however I
cannot delete the existing cephfs:
errors are as follows:
[root@ceph1 ~]# ceph fs rm cephfs2
Error EINVAL: all MDS daemons must be inactive before removing filesystem
I've tried killing the ceph-mds process, but this does not prevent the above
error.
I've also tried this, which also errors:
[root@ceph1 ~]# ceph mds stop 0
Error EBUSY: must decrease max_mds or else MDS will immediately reactivate
Right, so did you run "ceph mds set_max_mds 0" and then repeating the
stop command? :)
This also fail...
[root@ceph1 ~]# ceph-deploy mds destroy
[ceph_deploy.conf][DEBUG ] found configuration file at:
/root/.cephdeploy.conf
[ceph_deploy.cli][INFO ] Invoked (1.5.21): /usr/bin/ceph-deploy mds destroy
[ceph_deploy.mds][ERROR ] subcommand destroy not implemented
Am I doing the right thing in trying to wipe the original cephfs config
before attempting to use an erasure cold tier? Or can I just redefine the
cephfs?
Yeah, unfortunately you need to recreate it if you want to try and use
an EC pool with cache tiering, because CephFS knows what pools it
expects data to belong to. Things are unlikely to behave correctly if
you try and stick an EC pool under an existing one. :(
Sounds like this is all just testing, which is good because the
suitability of EC+cache is very dependent on how much hot data you
have, etc...good luck!
-Greg
many thanks,
Jake Grimmett
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Thanks for your help - much appreciated.
The "set_max_mds 0" command worked, but only after I rebooted the
server, and restarted ceph twice. Before this I still got an
"mds active" error, and so was unable to destroy the cephfs.
Possibly I was being impatient, and needed to let mds go inactive?
there were ~1 million files on the system.
[root@ceph1 ~]# ceph mds set_max_mds 0
max_mds = 0
[root@ceph1 ~]# ceph mds stop 0
telling mds.0 10.1.0.86:6811/3249 to deactivate
[root@ceph1 ~]# ceph mds stop 0
Error EEXIST: mds.0 not active (up:stopping)
[root@ceph1 ~]# ceph fs rm cephfs2
Error EINVAL: all MDS daemons must be inactive before removing filesystem
There shouldn't be any other mds servers running..
[root@ceph1 ~]# ceph mds stop 1
Error EEXIST: mds.1 not active (down:dne)
At this point I rebooted the server, did a "service ceph restart" twice.
Shutdown ceph, then restarted ceph before this command worked:
[root@ceph1 ~]# ceph fs rm cephfs2 --yes-i-really-mean-it
Anyhow, I've now been able to create an erasure coded pool, with a
replicated tier which cephfs is running on :)
*Lots* of testing to go!
Again, many thanks
Jake
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