[Lustre-discuss] Splitting lustre space

[Andreas Dilger]

On 2010-08-18, at 13:14, Kevin Van Maren wrote:
> David Noriega wrote:
>> But ultimately if I wanted two separate filesystems, I would need more
>> hardware? An OST can't be put into a general 'pool' for use between
>> the two?
> 
> You probably don't need more hardware, but you would have to decide 
> which file system each OST would serve -- it can only provide space to one file system.  So some of your OSTs would be for home and some for groups.  You would need to have 2 MDTs (if necessary, you could split/partition the MDT you have).

To clarify, it is NOT possible to have an OST in more than one filesystem, but it IS possible to have multiple OSTs (RAID LUNs + ldiskfs filesystem) on the same OSS node exported to different Lustre filesystems.

That said, this isn't a very common configuration except in the smallest of installations, since you now have a single point of failure for BOTH filesystems, and there is little value in e.g. sharing /home and /groups both across the same 10 OSS nodes, instead of having 4 OSS nodes for /home and 6 separate OSS nodes for /groups (or whatever split is needed for your usage).

For a small configuration it probably makes sense to share the space in a single filesystem as Kevin suggested.

Cheers, Andreas
--
Andreas Dilger
Lustre Technical Lead
Oracle Corporation Canada Inc.