Hi Stephen,
Burke, S (Stephen) a écrit :
>LHC Computer Grid - Rollout
>
>
>>[mailto:[log in to unmask]] On Behalf Of pierre girard said:
>>The solution consisting in adding CPU counts at Subcluster level,
>>proposed by stephen, should be the solution to our problem.
>>
>>
>
>The proposal has now been sent to the glue mailing list for discussion, but
>I wouldn't like to predict how long it will take before we see it in
>production!
>
>http://www.hicb.org/archives/glue-schema/2005/frm00001.html
>
>
Thanks for this link, it should be very interesting for us.
>
>
>>But a solution could be to sum systematically the CPUs of
>>each queue by site. Indeed, this value has the same meaning for all the
>>
>>
>sites.
>
>This doesn't really work for most sites. PBS sites generally have all the
>CPUs listed in every queue, so if there are ten queues you would overcount
>by a factor of ten.
>
>
Exactly. So what I meant is that the CPU concept defined from the queue
is not the same than the "real CPU" concept. It is what I call virtual
CPU instead of real CPU, but may be we should definitely use other term
for the queue CPU, something like "job entry point", to avoid any confusion.
As there is, for the moment, no sure way to compute real CPU count, I
then agree with you for getting it when the glue schema will allow a
site to directly provide it.
So, what I was simply suggesting is to compute what we have for the
moment, if we really want to compute something . ;)
And I think that we can already count the number of job entry points a
site provides to the grid, that is the sum of site queue CPUs.
What is the interest of this ? Certainly none for the moment, except
that this is a correct value which is uniformly computed over all the
sites. Possible comparison between sites could then be possible,
although I'm not sure that such a comparison would have a really
interest. But it could if site queues have been reasonably defined by
the site administrators.
Moreover, when we will be able to get the real CPU count, it could be
later used to compute an indicator of the quatility of service provided
by the sites. Indeed, we could then estimate something like the load
rate (?) of the site CPUs.
Indeed, I guess that a site which defines 10 queues on the same cluster
will not be able to provide the same quality of service than a site
which defines only 1 queue on the same kind of cluster. This is close to
the "overbooking" problem of an air passenger company ;). when all the
client arrive at same time...you are not able to live up to your offer,
and then client must wait.
But we are now quite away from our initial problem ;). And I think that
we finally all agree with the initial problem.
Pierre
>Stephen
>
>
>
--
______________________
Pierre GIRARD
Grid Computing Team Member
IN2P3/CNRS Computing Centre - Lyon (FRANCE)
http://cc.in2p3.fr
Tel. +33 4.78.93.08.80 | Fax. +33 4.72.69.41.70 | e-mail: [log in to unmask]
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