On 21/03/19 16:15 +0100, Dan van der Ster wrote:
On Thu, Mar 21, 2019 at 1:50 PM Tom Barron <tbarron@xxxxxxxxxx> wrote:
On 20/03/19 16:33 +0100, Dan van der Ster wrote:
>Hi all,
>
>We're currently upgrading our cephfs (managed by OpenStack Manila)
>clusters to Mimic, and want to start enabling snapshots of the file
>shares.
>There are different ways to approach this, and I hope someone can
>share their experiences with:
>
>1. Do you give users the 's' flag in their cap, so that they can
>create snapshots themselves? We're currently planning *not* to do this
>-- we'll create snapshots for the users.
>2. We want to create periodic snaps for all cephfs volumes. I can see
>pros/cons to creating the snapshots in /volumes/.snap or in
>/volumes/_nogroup/<uuid>/.snap. Any experience there? Or maybe even
>just an fs-wide snap in /.snap is the best approach ?
>3. I found this simple cephfs-snap script which should do the job:
>http://images.45drives.com/ceph/cephfs/cephfs-snap Does anyone have a
>different recommendation?
>
>Thanks!
>
>Dan
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Dan,
Manila of course provides users with self-service file share snapshot
capability with quota control of the snapshots. I'm sure you are
aware of this but just wanted to get it on record in this thread.
Snapshots are not enabled by default for cephfs native or cephfs with
nfs in Manila because cephfs snapshots were experimental when the
cephfs driver was added and we maintain backwards compatability in
the Manila configuration. To enable, one sets:
cephfs_enable_snapshots = True
in the configuration stanza for cephfsnative or cephfsnfs back end.
Also, the ``share_type`` referenced when creating shares (either
explicitly or the default one) needs to have the snapshot_support
capability enabled -- e.g. the cloud admin would (one time) issue a
command like the following:
$ manila type-key <default-share-type> set snapshot_support=True
With this approach either the user or the administrator can create
snapshots of file shares.
Dan, I expect you have your reasons for choosing to control snapshots
via a script that calls cephfs-snap directly rather than using Manila
-- and of course that's fine -- but if you'd share them it will help
us Manila developers consider whether there are use cases that we are
not currently addressing that we should consider.
Hi Tom, Thanks for the detailed response.
The majority of our users are coming from ZFS/NFS Filers, where
they've gotten used to zfs-auto-snapshots, which we create for them
periodically with some retention. So accidental deletions or
overwrites are never a problem because they can quickly access
yesterday's files.
So our initial idea was to replicate this with CephFS/Manila.
I hadn't thought of using the Manila managed snapshots for these
auto-snaps -- it is indeed another option. Have you already considered
Manila-managed auto-snapshots?
I've added this topic to our etherpad list [1] for the upcoming PTG.
Today one could make a script that interacts with the manila API to
create snaps periodically but they would be done one-by-one (even if
in parallel) rather than atomically for the whole file system or at
the root of the all the users shares.
Please feel free to adjust they way I've framed the issue in that
etherpad so that it is suitable.
Otherwise, I wonder if CephFS would work well with both the fs-wide
auto-snaps *and* user-managed Manila snapshots. Has anyone tried such
a thing?
I haven't and would be interested in hearing as well. Manila also
supports NetApp and ZFS back ends so I'll ask more generally as well
as for CephFS.
-- Tom
[1] https://etherpad.openstack.org/p/manila-denver-train-ptg-planning
Thanks!
dan
Thanks,
-- Tom Barron
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