[Gluster-users] snapshots questions

[Vinayak Papnoi]

Comments inline.

Regards,

Vinayak Papnoi

Associate Quality Engineer

Red Hat <https://www.redhat.com/>

vpapnoi at redhat.com
M: 91-9702904495     IM: vpapnoi
<https://www.redhat.com/>


On Wed, Jun 26, 2019 at 6:12 PM Dmitry Filonov <filonov at hkl.hms.harvard.edu>
wrote:

> Hi,
>  am really new to gluster and have couple question that I hope will be
> really easy to answer. Just couldn't find anything on that myself.
>
> I did set up replica 3 gluster over 3 nodes with 2TB SSD in each node.
> To have snapshot functionality I have created thin pool of the size of VG
> (1.82TB) and then 1.75TB thin LVM inside on each of the bricks.
> It worked just fine until I scheduled creating hourly and daily snapshots
> on that gluster volume. In less than 2 days my thin volume got full and
> crashed.
> Not refused creating new snapshots, but just died as LVM couldn't perform
> any operations there anymore.
> So my first question is how to prevent this from happening. I could create
> smaller thin LVM, but I still have no control how much space I would need
> for snapshots. I was hoping to see some warnings and errors while creeating
> snapshots, but not failed LVM/Gluster.
>

Newly created snapshots will occupy some data and metadata space in LVM. So
the more snapshots you have, the more space will be utilized.


> The second question is related but not that important. Is there a way to
> schedule snapshot removal in cron? gluster snapshot delete requires
> interactive confirmation and I don't see any flag to auto-confirm snapshot
> removal.
>

As of now, No. There isn't any option to schedule a removal of the
snapshot. As for auto-confirmation of any command in gluster,
'--mode=script' at the end of the command should work.
Although, there is a snapshot config option "*auto-delete*" which, when
enabled, will *delete* the oldest snapshot *after crossing the
snap-max-soft-limit* (which is a set percentage of the
snap-max-hard-limit).

# gluster snapshot config

Snapshot System Configuration:
snap-max-hard-limit : 256
snap-max-soft-limit : 90%
auto-delete : enable
activate-on-create : disable

Snapshot Volume Configuration:

Volume : <volname>
snap-max-hard-limit : 256
Effective snap-max-hard-limit : 256
Effective snap-max-soft-limit : 230 (90%)

Usage:
snapshot config [volname] ([snap-max-hard-limit <count>]
[snap-max-soft-limit <percent>]) | ([auto-delete <enable|disable>])|
([activate-on-create <enable|disable>])


> Thank you,
>
> Fil
>
> --
> Dmitry Filonov
> Linux Administrator
> SBGrid Core | Harvard Medical School
> 250 Longwood Ave, SGM-114
> Boston, MA 02115
> _______________________________________________
> Gluster-users mailing list
> Gluster-users at gluster.org
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