[gpfsug-discuss] How to shrink GPFS on DSSG's?

Jonathan Buzzard jonathan.buzzard at strath.ac.uk
Mon Jun 20 19:40:16 BST 2022

On 20/06/2022 19:04, Jaime Pinto wrote:
> I'm wondering if it's possible to shrink GPFS gracefully.

Yes absolutely, been possible since at least version 2.2 and probably older.

> I've seen some 
> references to that effect on some presentations, however I can't find 
> detailed instructions on any formal IBM documentation on how to do it.

Use mmdeldisk to remove the NSD(s) from a file system. This will take a 
while so I recommend in the *STRONGEST* possible terms running it in a 
screen or tmux session. By a while it could be days or even weeks 
depending on how much data needs to be moved about.

Once you have removed the NSD's from a file system then you can use 
mmdelnsd to wipe the NSD descriptors from the disks if necessary.

> About 3 years ago we launched a new GPFS deployment with 3 DSS-G 
> enclosures (9.6PB usable).
> Some 1.5 years later we added 2 more enclosures, for a total of 16PB, 
> and only 7PB occupancy so far.
> Basically I'd like to return to the original 3 enclosures, and still 
> maintain the (8+2p) parity level.
> Any suggestions?

Not being sarky but really use Google. Say "gpfs remove nsd from file 
system" and select the first link!


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

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