Any guidance on this?  I have osd_snap_trim_sleep set to 1 and it seems to have 
tempered some of the issues but its still bad enough that NFS storage off RBD 
volumes become unavailable for over 3 minutes.

It seems that the activity which the snapshot deletes are actioned triggers 
massive disk load for around 30 minutes.  The logs show OSDs marking each other 
out, OSDs complaining they are wrongly marked out and blocked requests errors 
for around 10 minutes at the start of this activity.

Is there any way to throttle snapshot deletes to make them much more of a 
background activity?  It really should not make the entire platform unusable 
for 10 minutes.

> -----Original Message-----
> From: ceph-users [] On Behalf Of
> Adrian Saul
> Sent: Wednesday, 6 July 2016 3:41 PM
> To: ''
> Subject: [ceph-users] Snap delete performance impact
> I recently started a process of using rbd snapshots to setup a backup regime
> for a few file systems contained in RBD images.  While this generally works
> well at the time of the snapshots there is a massive increase in latency (10ms
> to multiple seconds of rbd device latency) across the entire cluster.  This 
> has
> flow on effects for some cluster timeouts as well as general performance hits
> to applications.
> In research I have found some references to osd_snap_trim_sleep being the
> way to throttle this activity but no real guidance on values for it.   I also 
> see
> some other osd_snap_trim tunables  (priority and cost).
> Is there any recommendations around setting these for a Jewel cluster?
> cheers,
>  Adrian
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