[Lustre-discuss] more on MGS and MDT separation

[David Dillow]

On Fri, 2009-10-23 at 03:00 -0600, Andreas Dilger wrote:
> On 2009-10-22, at 13:41, Ms. Megan Larko wrote:
> > Additionally in Lustre-discuss Digest Vol 45 Issue 36 A. Dilger  
> > opined:
> > "...128Mb is the max size the MGS would ever need."
> >
> > Wow!  That is small.  I know the MGS does not store the sort of data
> > retained on an MDT for a multi-Tb filesystem, but really 128Mb max
> > would be used?
> 
> 
> I honestly don't have much data on this, so I can't say with absolute
> certainty whether that is the max.  There are only a handful of smallish
> config files per server, and one for all of the clients.  The MGS  
> doesn't
> need very much space.
> 
> Maybe someone with access to ORNL Spider (largest Lustre filesystem) can
> comment on how much space is used in the /CONFIGS/ directory?

With one filesystem configured -- 672 OSTs -- CONFIGS contains 676 files
and uses 124 MB or so.

We expect to have another few more filesystems using this MGS, so
extrapolating from current usage I guess we'll top out at around 496 MB
for the large filesystems, and perhaps a few MB more for the smaller
ones.
-- 
Dave Dillow
National Center for Computational Science
Oak Ridge National Laboratory
(865) 241-6602 office