[gpfsug-discuss] snapshots & tiering in a busy filesystem

[Sobey, Richard A]

Embarrassingly I don’t know how to do that scientifically. I can tell you latency of the storage system which at a very simplistic snapshot is averaging around 2ms. We are not using SSD for metadata but 10K SAS.

From: gpfsug-discuss-bounces at spectrumscale.org [mailto:gpfsug-discuss-bounces at spectrumscale.org] On Behalf Of J. Eric Wonderley
Sent: 22 March 2017 13:41
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] snapshots & tiering in a busy filesystem

The filesystem I'm working with has about 100M files and 80Tb of data.

What kind of metadata latency do you observe?
I did a mmdiag --iohist and filtered out all of the md devices and averaged over reads and writes.  I'm seeing ~.28ms on a one off dump.  The pure array which we have is 10G iscsi connected and is reporting average .25ms.

On Wed, Mar 22, 2017 at 6:47 AM, Sobey, Richard A <r.sobey at imperial.ac.uk<mailto:r.sobey at imperial.ac.uk>> wrote:
We’re also snapshotting 4 times a day. Filesystem isn’t tremendously busy at all but we’re creating snaps for each fileset.

[root at cesnode tmp]# mmlssnapshot gpfs | wc -l
6916

From: gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org> [mailto:gpfsug-discuss-bounces at spectrumscale.org<mailto:gpfsug-discuss-bounces at spectrumscale.org>] On Behalf Of J. Eric Wonderley
Sent: 20 March 2017 14:03
To: gpfsug main discussion list <gpfsug-discuss at spectrumscale.org<mailto:gpfsug-discuss at spectrumscale.org>>
Subject: [gpfsug-discuss] snapshots & tiering in a busy filesystem

I found this link and it didn't give me much hope for doing snapshots & backup in a home(busy) filesystem:
http://www.spectrumscale.org/pipermail/gpfsug-discuss/2013-February/000200.html
I realize this is dated and I wondered if qos etc have made is a tolerable thing to do now.  Gpfs I think was barely above v3.5 in mid 2013.

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