[gpfsug-discuss] Mass UID migration suggestions

[Jonathan Buzzard]

On Wed, 2017-08-02 at 21:03 -0400, Aaron Knister wrote:
> Oh, the one *huge* gotcha I thought I'd share-- we wrote a perl script 
> to drive the migration and part of the perl script's process was to 
> clone quotas from old uid numbers to the new number. I upset our GPFS 
> cluster during a particular migration in which the user was over the 
> grace period of the quota so after a certain point every chown() put the 
> destination UID even further over its quota. The problem with this being 
> that at this point every chown() operation would cause GPFS to do some 
> cluster-wide quota accounting-related RPCs. That hurt. It's worth making 
> sure there are no quotas defined for the destination UID numbers and if 
> they are that the data coming from the source UID number will fit.

For similar reasons if you are doing a restore of a file system (any
file system for that matter not just GPFS) for whatever reason, don't
turn quotas back on till *after* the restore is complete. Well unless
you can be sure a user is not going to go over quota during the restore.
However as this is generally not possible to determine you end up with
no quota's either set/enforced till the restore is complete.

JAB.

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