[gpfsug-discuss] default owner and group for POSIX ACLs

[Skylar Thompson]

On Wed, Oct 16, 2019 at 09:32:50PM +0000, Jonathan Buzzard wrote:
> On 15/10/2019 16:41, Simon Thompson wrote:
> > I thought Spectrum Protect didn't actually backup again on a file
> > owner change. Sure mmbackup considers it, but I think Protect just
> > updates the metadata. There are also some other options for dsmc that
> > can stop other similar issues if you change ctime maybe.
> > 
> > (Other backup tools are available)
> > 
> 
> It certainly used too. I spent six months carefully chown'ing files one 
> user at a time so as not to overwhelm the backup, because the first 
> group I did meant no backup for about a week...
> 
> I have not kept a close eye on it and have just worked on the assumption 
> for the last decade of "don't do that". If it is no longer the case I 
> apologize for spreading incorrect information.

TSM can store some amount of metadata in its database without spilling over
to a storage pool, so whether a metadata update is cheap or expensive
depends not just on ACLs/extended attributes but also the directory entry
name length. It can definitely make for some seemingly non-deterministic
backup behavior.

-- 
-- Skylar Thompson (skylar2 at u.washington.edu)
-- Genome Sciences Department, System Administrator
-- Foege Building S046, (206)-685-7354
-- University of Washington School of Medicine