[Lustre-devel] Fast checkpoints in Lustre today, at essentially zero cost.

[Andreas Dilger]

On Mar 05, 2009  15:35 -0500, Oleg Drokin wrote:
> On Mar 5, 2009, at 3:00 PM, Andreas Dilger wrote:
>> We don't need to go to the sub-optimal striping to get this result,
>> as that causes not only lots of seeking on the OSTs, but also requires
>> the clients to get locks on every OST.  Instead it is possible today
>> to just increase this limit to be much larger via /proc tunings on
>> the client for testing (assume 1/2 of RAM is large enough):
>> client# lctl set_param osc.*.max_dirty_mb=${ramsize/2}
>
> Of course! But I am speaking of a situation like say ORNL, where
> users cannot control this setting directly.

But if this is just testing, then we may as well avoid the extra overhead
and apples-to-oranges comparison of single-stripe vs. many-stripe files
and allow single-stripe files to cache a lot of data.

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