[Lustre-discuss] mixed oss/ost performance question

[Andreas Dilger]

On 2011-03-04, at 3:14 PM, Samuel Aparicio wrote:
> I have a general question about mixing of osts with slower or faster backing storage.  we have a fair number of slower "legacy" disk pools and a bunch of newer faster ones.  the fast and slow are aggregated separately to provide OST storage targets with a uniform speed characteristic (slow or fast),
> 
> my question is whether it would be better to make two separate filesystems (say lustre1 and lustre2) with the slow and fast OSTs respectively,
> or is it reasonable to have these all under one filesystem.

It depends today on the sophistication of your users.  It is possible to split different storage classes with OST pools (see the commands "lctl pool_add" and
"lfs setstripe -p"), but these are "optional" separations today.  If users don't specify any pool then the default is to use all OSTs (mixing fast and slow storage).  You CAN specify default pools on a per-directory basis, but this only applies to newly-created files.

Cheers, Andreas
--
Andreas Dilger 
Principal Engineer
Whamcloud, Inc.