On 15 April 2011 10:48, Peter Grandi <[log in to unmask]> wrote:
> BTW, in GraemeS' presentation as to the overall picture I find on page 28 "Disk space at T1s is now even tighter than T2s" and on page 29 "Just not enough T2 CPUs which could eat through the work" which seems to indicate that T2 are more CPU than disk bound for ATLAS.
Hi Peter,
So, "disk" means different things in different contexts.
Graeme's presentation uses "disk" to mean "storage in an SE".
Be careful when using the term "disk bound" in this context, therefore
- T2s are limited in the number of jobs they can run by the number of
CPUs (which is what Graeme's commenting on), but the performance of
any particular analysis job on a T2 node is almost certainly IO bound,
not CPU bound.
In the wider context of disk performance at T2s, because many ATLAS
jobs stage data from the storage to the worker node's local disk, it's
the performance of the disk at the WN which is critical, not that in
the SE (which, for most large sites, will be distributing load over
(24 to 36 disks) * ( 10 to 30 server) ).
Sam
|