[gpfsug-discuss] Question on changing mode on many files

Simon Thompson s.j.thompson at bham.ac.uk
Tue Dec 7 14:55:15 GMT 2021

Or add:
  UPDATECTIME               yes

To you dsm.opt file to skip checking for those updates and don’t back them up again.

Actually I thought TSM only updated the metadata if the mode/owner changed, not re-backed the file…


From: gpfsug-discuss-bounces at spectrumscale.org <gpfsug-discuss-bounces at spectrumscale.org> on behalf of Jonathan Buzzard <jonathan.buzzard at strath.ac.uk>
Date: Tuesday, 7 December 2021 at 14:29
To: gpfsug-discuss at spectrumscale.org <gpfsug-discuss at spectrumscale.org>
Subject: Re: [gpfsug-discuss] Question on changing mode on many files
On 07/12/2021 14:01, Frederick Stock wrote:

> If you are running on a more recent version of Scale you might want to
> look at the mmfind command.  It provides a find-like wrapper around the
> execution of policy rules.

I am not sure that will be any faster than a "chmod -R" as it will exec
millions of instances of chmod. What you gain on the swings you are
going to loose on the roundabouts.

TL;DR is you want to change permissions on millions of files expect it
to take a considerable period of time. Even a modern NVMe SSD probably
does around 50k IOPS per second, so best case scenario is one million
files taking 40 seconds, at one read and one write per file and that is
frankly unlikely.

Also get ready to back them up again.


Jonathan A. Buzzard                         Tel: +44141-5483420
HPC System Administrator, ARCHIE-WeSt.
University of Strathclyde, John Anderson Building, Glasgow. G4 0NG
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