Lustre discuss - Dec 2009 - New lustre setup - opinions sought

Hi,
         We are in the processes of setting up 2 filesystems using lustre.
         The first one will be based on 10K RPM SAS drives (much faster -
scratch space),
          Second would be on 1TB SATA drives (slower one - user''s
home).
         As I can see, there are two options :
         1.Create two separate filesystems with multihomed MDS
         2. A single filesystem with 2 OST pools with different stride
size(one SAS and one SATA based).
            Create 2 directories in the lustre FS root by name
''scratch'' &
''home'' and set stripe pattern and stripe size accordingly for
scratch(SAS)
and home(SATA).

Any pointers to pros and cons for the above two setup.
Other thing is that we do not want files to be stripped across pool. Is
there anything that would enforce this.

--Reject the basic assumptions of civilization,
  especially the importance of materiel possessions.--
--
Rishi Pathak
National PARAM Supercomputing Facility
Centre for Development of Advanced Computing
Ganeshkhind Road
Pune University Campus
PUNE-Maharastra
Phone :      +91-20-25704197 extension-197
                 +91-20-25704354 extension-354
Cell : +919766233322
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On 2009-12-01, at 03:30, rishi pathak wrote:
>   We are in the processes of setting up 2 filesystems using lustre.
>   The first one will be based on 10K RPM SAS drives (much faster -  
> scratch space),
>   Second would be on 1TB SATA drives (slower one - user''s home).
Actually, I would suggest the reverse - SAS drives for the smaller  
home filesystem, and the larger SATA drives for the scratch  
filesystem.  Users need better interactive performance and generally  
use smaller files, while the scratch filesystem is used by batch jobs  
that need higher throughput but does not notice higher latency.

Depending on how large you want to make your home filesystem, you  
might consider using RAID-1 instead of RAID-6 to further improve the  
filesystem performance.
>  As I can see, there are two options :
>     1.Create two separate filesystems with multihomed MDS
>     2. A single filesystem with 2 OST pools with different stride  
> size(one SAS and one SATA based).
>             Create 2 directories in the lustre FS root by name  
> ''scratch'' & ''home'' and set stripe
pattern and stripe size
> accordingly for scratch(SAS) and home(SATA).
>
> Any pointers to pros and cons for the above two setup.
> Other thing is that we do not want files to be stripped across pool.  
> Is there anything that would enforce this.
Currently it is not possible to use pools to _deny_ access to specific  
OSTs, though this would be an interesting feature.  From your  
description, I can''t see any benefit to having these different OSTs in
the same filesystem

Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.