On Tue, 26 May 2009, David Lawrence wrote:
Dear David et al.,
okay I cannot keep myself from replying. For hermes we need for a fully
reconstructed event in Geant-3 between 0.5 to 2.5 s, at rhic Au on Au an
event takes a between 1 - 2 min CPU time.
So I'm not sure what you mean it costs nothing to produce MC events. It
costs time and the rule of thum is at least 10 times the MC statistics
compared to the data. So with the data statistics GlueX is expecting you
will need continously to generate MC to reach 10 times the data statistics.
This udst need to be stored somewhere, so you will need disk-space or
tape-space.
I would revise the xls sheets to include this in your estimate.
I know the only valid comparision is CLAS, I have no idea what they do,
but from my limited knowledge on CLAS I know they are normally not heavy
on MC studies.
Cheers elke
Date: Tue, 26 May 2009 15:34:42 -0400
From: David Lawrence <davidl@jlab.org>
To: Mark M. Ito <marki@jlab.org>
Cc: HallD Software Group <halld-offline@jlab.org>
Subject: Re: Request for additional work space for Hall D
Hi Mark,
This may be a little late, but here are the latest spreadsheet (and it's
explanation) used to compute the predicted GlueX disk space. The main thing
you'll notice is that there is virtually no disk space allocated for
simulation. This was mainly due to a calculation that it costs more to store
the simulated data than reproduce it. As such, we wanted the IT division to
focus their budget on more CPU power for the farm as opposed to work disk
space. This is not to say that philosophy should still be followed, just that
that was the motivation in the past. You are likely to get questions from
Sandy and Chip referring back to the spreadsheet.
Regards,
-David
Mark M. Ito wrote:
> In recent months we have run out of space on our works disk from time to
> time. Our activity generating and reconstructing simulated data is ramping
> up. We discussed the situation in the Hall D Offline Meeting and we would
> like request more space. Our current allocation is 2.7 TB. We request that
> this be increased to 5 TB as soon as possible and that the total be
> increased to about 10 TB over the next year.
>
> Once in operation, the GlueX detector will generate a large volume of data.
> To be ready to analyze real data once it comes in we will have to generate
> large amounts of simulated data to develop and test all the of necessary
> tools well in advance of the arrival of real data. As we approach
> operations we will likely need an amount of space equal to or exceeding the
> amount used by Hall B (about 35 TB). Recall that raw data is generally not
> stored on the work disks in any case, work space is used for intermediate
> files needed to analyze raw or simulated data. The fact that GlueX has not
> taken real data yet does not imply our current disk needs are
> insignificant. We note that this request is quite modest when compared to
> the total amount of work disk space deployed at present.
>
>
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12 GeV Computing Worksheetsv2.xls