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

Jonathan Buzzard jonathan.buzzard at strath.ac.uk
Tue Dec 7 14:28:54 GMT 2021

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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