[gpfsug-discuss] gpfs snapshots

Tue Sep 13 22:47:02 BST 2016

We do have a general-purpose scheduler on the books as an item that is
needed for a future release and as Yuri mentioned it would be cluster wide
to avoid the single point of failure with tools like Cron.  However, it's
one of many things we want to try to get into the product and so we don't
have any definite timeline yet.

Thanks,

John

John T. Olson, Ph.D., MI.C., K.EY.
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or Seinfeld.

From:	"Simon Thompson (Research Computing - IT Services)"
            <S.J.Thompson at bham.ac.uk>
To:	gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:	09/13/2016 02:22 PM
Subject:	Re: [gpfsug-discuss] gpfs snapshots
Sent by:	gpfsug-discuss-bounces at spectrumscale.org

I thought the GUI implemented some form of snapshot scheduler. Personal
opinion is that is the wrong place and I agree that is should be core
functionality to ensure that the scheduler is running properly.

But I would suggest that it might be more than just snapshots people might
want to schedule. E.g. An ilm pool flush.

Simon
________________________________________
From: gpfsug-discuss-bounces at spectrumscale.org
[gpfsug-discuss-bounces at spectrumscale.org] on behalf of Yuri L Volobuev
[volobuev at us.ibm.com]
Sent: 13 September 2016 21:51
To: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] gpfs snapshots

Hi Jez,

It sounds to me like the functionality that you're _really_ looking for is
an ability to to do automated snapshot management, similar to what's
available on other storage systems. For example, "create a new snapshot of
filesets X, Y, Z every 30 min, keep the last 16 snapshots". I've seen many
examples of sysadmins rolling their own snapshot management system along
those lines, and an ability to add an expiration string as a snapshot
"comment" appears to be merely an aid in keeping such DIY snapshot
management scripts a bit simpler -- not by much though. The end user would
still be on the hook for some heavy lifting, in particular figuring out a
way to run an equivalent of a cluster-aware cron with acceptable fault
tolerance semantics. That is, if a snapshot creation is scheduled, only one
node in the cluster should attempt to create the snapshot, but if that node
fails, another node needs to step in (as opposed to skipping the scheduled
snapshot creation). This is doable outside of GPFS, of course, but is not
trivial. Architecturally, the right place to implement a fault-tolerant
cluster-aware scheduling framework is GPFS itself, as the most complex
pieces are already there. We have some plans for work along those lines,
but if you want to reinforce the point with an RFE, that would be fine,
too.

yuri

[Inactive hide details for Jez Tucker ---09/13/2016 02:10:31 AM---Hey Yuri,
Perhaps an RFE here, but could I suggest there is]Jez Tucker ---09/13/2016
02:10:31 AM---Hey Yuri, Perhaps an RFE here, but could I suggest there is
much value in

From: Jez Tucker <jtucker at pixitmedia.com>
To: gpfsug-discuss at spectrumscale.org,
Date: 09/13/2016 02:10 AM
Subject: Re: [gpfsug-discuss] gpfs snapshots
Sent by: gpfsug-discuss-bounces at spectrumscale.org

________________________________

Hey Yuri,

  Perhaps an RFE here, but could I suggest there is much value in adding a
-c <comment> option to mmcrsnapshot?

Use cases:

mmcrsnapshot myfsname @GMT-2016.09.13-10.00.00 -j myfilesetname -c "Before
phase 2"

and

mmcrsnapshot myfsname @GMT-2016.09.13-10.00.00 -j myfilesetname -c
"expire:GMT-2017.04.21-16.00.00"

Ideally also: mmcrsnapshot fs1
fset1:snapA:expirestr,fset2:snapB:expirestr,fset3:snapC:expirestr

Then it's easy to iterate over snapshots and subsequently mmdelsnapshot
snaps which are no longer required.
There are lots of methods to achieve this, but without external databases /
suchlike, this is rather simple and effective for end users.

Alternatively a second comment like -expire flag as user metadata may be
preferential.

Thoughts?

Jez

On 13/09/16 05:32, Valdis.Kletnieks at vt.edu<mailto:Valdis.Kletnieks at vt.edu>
wrote:

On Tue, 13 Sep 2016 00:30:19 +0200, Lukas Hejtmanek said:
I guess we could reach snapid 100,000.

It probably stores the snap ID as a 32 or 64 bit int, so 100K is peanuts.

What you *do* want to do is make the snap *name* meaningful, using
a timestamp or something to keep your sanity.

mmcrsnapshot fs923 `date +%y%m%d-%H%M`   or similar.
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--
Jez Tucker
Head of Research & Product Development
Pixit Media
www.pixitmedia.com<http://www.pixitmedia.com/>

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