Mike Kenyon wrote:
> Hi Ben,
>
> Responses inline
>
> On 26 June 2010 10:05, Ben Waugh <[log in to unmask]> wrote:
>> There are of course other factors affecting job throughput, including
>> hard disks and RAM. Is there some way of measuring the effect of
>> these, or would you just set a minimum requirement on both and then
>> maximise the HEPSPEC? If you would take the latter approach, what is a
>> sensible trade-off between disk performance and price? Presumably
>> 10kRPM SAS disks will be better than 7.5kRPM SATA, but maybe a striped
>> pair of slow disks would be an alternative? And how much disk space do
>> you allow per CPU core?
>
> At Glasgow, we've opted to buy our latest generation of WNs with 2 x
> 15kRPM disks, and will configure them in a RAID0 array. This followed
> extensive testing of various WN configs, using a range of SSDs (X25's
> and Kingston Value) versus RAIDED disks. We found the best "bang per
> buck" was given by the 2 HDD solution.
>
I don't think it applies in this case, but it will for QMUL - and we are
going through a similar exercise.
The bang for buck figure is presumably based on the assumption that jobs
will copy input files to the worker node disks and this is what stresses
the disks. That will not be the case at sites using Lustre/GPFS for
their SRM. QMUL is working on the assumption that a standard SATA disk
is fine for that.
Chris
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