[gpfsug-discuss] GPFS Independent Fileset Limit vs Quotas?

Peinkofer, Stephan Stephan.Peinkofer at lrz.de
Fri Aug 17 12:39:54 BST 2018


Dear Marc,


well as I think I cannot simply "move" dependent filesets between independent ones and our customers must have the opportunity to change data protection policy for their Containers at any given time, I cannot map them to a "backed up" or "not backed up" independent fileset.


So how much performance impact is lets say 1-10 exclude.dir directives per independent fileset?


Many thanks in advance.

Best Regards,

Stephan Peinkofer


________________________________
From: gpfsug-discuss-bounces at spectrumscale.org <gpfsug-discuss-bounces at spectrumscale.org> on behalf of Marc A Kaplan <makaplan at us.ibm.com>
Sent: Tuesday, August 14, 2018 5:31 PM
To: gpfsug main discussion list
Subject: Re: [gpfsug-discuss] GPFS Independent Fileset Limit vs Quotas?

True, mmbackup is designed to work best backing up either a single independent fileset or the entire file system.  So if you know some filesets do not need to be backed up, map them to one or more indepedent filesets that will not be backed up.

mmapplypolicy is happy to scan a single dependent fileset, use option --scope fileset and make the primary argument the path to the root of the fileset you wish to scan.   The overhead is not simply described.   The directory scan phase will explore or walk the (sub)tree in parallel with multiple threads on multiple nodes, reading just the directory blocks that need to be read.

The inodescan phase will read blocks of inodes from the given inodespace ...  since the inodes of dependent filesets may be "mixed" into the same blocks as other dependend filesets that are in the same independent fileset, mmapplypolicy will incur what you might consider "extra" overhead.




From:        "Peinkofer, Stephan" <Stephan.Peinkofer at lrz.de>
To:        gpfsug main discussion list <gpfsug-discuss at spectrumscale.org>
Date:        08/14/2018 12:50 AM
Subject:        Re: [gpfsug-discuss] GPFS Independent Fileset Limit vs Quotas?
Sent by:        gpfsug-discuss-bounces at spectrumscale.org
________________________________



Dear Marc,


If you "must" exceed 1000 filesets because you are assigning each project to its own fileset, my suggestion is this:

Yes, there are scaling/performance/manageability benefits to using mmbackup over independent filesets.

But maybe you don't need 10,000 independent filesets --
maybe you can hash or otherwise randomly assign projects that each have their own (dependent) fileset name to a lesser number of independent filesets that will serve as management groups for (mm)backup...

OK, if that might be doable, whats then the performance impact of having to specify Include/Exclude lists for each independent fileset in order to specify which dependent fileset should be backed up and which one not?
I don’t remember exactly, but I think I’ve heard at some time, that Include/Exclude and mmbackup have to be used with caution. And the same question holds true for running mmapplypolicy for a “job” on a single dependent fileset? Is the scan runtime linear to the size of the underlying independent fileset or are there some optimisations when I just want to scan a subfolder/dependent fileset of an independent one?

Like many things in life, sometimes compromises are necessary!

Hmm, can I reference this next time, when we negotiate Scale License pricing with the ISS sales people? ;)

Best Regards,
Stephan Peinkofer
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