It's fixed since v0.94.6, http://ceph.com/releases/v0-94-6-hammer-released/
- fs: CephFS restriction on removing cache tiers is overly strict (issue#11504, pr#6402, John Spray)
but you have to make sure your release patched.
2017-01-10 16:52 GMT+08:00 Nick Fisk <nick@xxxxxxxxxx>:
> -----Original Message-----
> From: ceph-users [mailto:ceph-users-bounces@lists.ceph.com ] On Behalf Of Wido den Hollander
> Sent: 10 January 2017 07:54
> To: ceph new <ceph-users@xxxxxxxxxxxxxx>; Stuart Harland <s.harland@livelinktechnology.net >
> Subject: Re: Write back cache removal
>
>
> > Op 9 januari 2017 om 13:02 schreef Stuart Harland <s.harland@livelinktechnology.net >:
> >
> >
> > Hi,
> >
> > We’ve been operating a ceph storage system storing files using librados (using a replicated pool on rust disks). We implemented a
> cache over the top of this with SSDs, however we now want to turn this off.
> >
> > The documentation suggests setting the cache mode to forward before draining the pool, however the ceph management
> controller spits out an error about this saying that it is unsupported and hence dangerous.
> >
>
> What version of Ceph are you running?
>
> And can you paste the exact command and the output?
>
> Wido
Hi Wido,
I think this has been discussed before and looks like it might be a current limitation. Not sure if it's on anybody's radar to fix.
https://www.mail-archive.com/ceph-users@xxxxxxxxxxxxxx/ msg24472.html
Nick
>
> > The thing is I cannot really locate any documentation as to why it’s considered unsupported and under what conditions it is expected
> to fail: I have read a passing comment about EC pools having data corruption, but we are using replicated pools.
> >
> > Is this something that is safe to do?
> >
> > Otherwise I have noted the read proxy mode of cache tiers which is documented as a mechanism to transition from write back to
> disabled, however the documentation is even sparser on this than forward mode. Would this be a better approach if there is some
> unsupported behaviour in the forward mode cache option?
> >
> > Any thoughts would be appreciated - we really cannot afford to corrupt the data, and I really do not want to have to do some
> manual software based eviction on this data.
> >
> > regards
> >
> > Stuart
> >
> >
> > − Stuart Harland:
> > Infrastructure Engineer
> > Email: s.harland@livelinktechnology.net <mailto:s.harland@livelinktechnology.net >
> >
> >
> >
> > LiveLink Technology Ltd
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> > PO9 1BS
> >
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