Hi,
I asked about the memory since some people wanted an official answer but
there are two answers... the official one is 2GB per job slot is still
the requirement but the unnoficial one is that for run2 they'll need
more 3-4GB per job slot and to reccomend sites that if they can afford it.
cheers
alessandra
On 12/11/2013 16:15, Alastair Dewhurst wrote:
> Hi
>
> I am sorry for not being more prepared earlier for the 11am OPs meeting. I have given links to the various sources I have used. The ATLAS links are unfortunately protected (for legitimate reasons) and I can't really send round copies to everyone. However if you really want to read up, there is probably an ATLAS user at your site who you can ask.
>
> On page 15 in [1] there is a plot showing the ratio of storage compared to CPU seconds provided to ATLAS for all sites. The ratio is surprising stable over the vast majority of sites. This ratio is 7 HepSpec06 for each TB of storage provided, or approximately 1 job slot per TB of storage.
>
> In [2] Borut goes into more detail about ATLAS future plans:
> "Our resource planning is based upon the physics programme that can be accomplished within achievable pledged resources, corresponding to a ‘flat’ spending budget, while we hope that our centres and funding agencies will continue to provide ATLAS with the invaluable resources beyond those pledged that will allow us to accomplish an optimal research programme and physics productivity"
>
> The model then assumes that with a flat budget:
> CPU will increase by a factor of 1.2 per year
> Disk space will increase by a factor of 1.15 per year
> so over time, the HEPSpec to storage ratio will grow.
>
> What confuses me, and I can only assume this has been done for political reasons, is that the official request lags behind this expected growth for the next 2 years but then catches up by the time we reach 2017. So for example in 2015 the request for Tier 2s appears to be 55PB which isn't much different from now. However ATLAS are expecting 65PB available. However by 2017 the request is 98PB which is the ~1.15^4 the 2013 figure.
>
> On slide 8 in [2] it also mentions that ~15% of CPU resources were spent on MC generation and this could be moved to opportunistic HPC resources. Most of this 15% would have been done at Tier 2s as it doesn't require any particular input files. There is no particular time line for when this will happen although there was a talk at the ATLAS Weekly meeting today [5] so it is a very active area. I would therefore recommend keeping the ratio of disk to CPU roughly the same as it is now.
>
> In terms of memory requirements per jobs, there is still an aim to keep jobs to 2GB per slot. However for every improvement made there are another 2 reasons to increase the memory foot print. I would recommend what Martin Bly decided for the Tier 1 which was 4 GB per slot. Also, while not wishing to comment on LHCb's plans, they do occasionally need to use 6GB per job for their problematic work flows at RAL, so for sites planning on hosting LHCb data, you have been warned!
>
> I have included two other links, Eric Lancon's talk [3] contains pretty much the same as Borut's two talks, but in a more condensed form. If you want lots of detail, [4] contains the draft computing model for run 2 in 153 pages! I believe this is not restricted to just ATLAS.
>
> I hope this helps. I will ask Roger Jones for his comments as well.
>
> Alastair
>
>
> [1] Borut, WLCG workshop:
> https://indico.cern.ch/getFile.py/access?contribId=12&sessionId=1&resId=0&materialId=slides&confId=251191
>
> [2] Borut, physics coordination:
> https://indico.cern.ch/getFile.py/access?contribId=3&resId=0&materialId=slides&confId=270627
>
> [3] Eric Lancon, computing model for Run 2
> https://indico.cern.ch/getFile.py/access?contribId=46&sessionId=11&resId=0&materialId=slides&confId=250727
>
> [4] WLCG TDR:
> https://indico.cern.ch/getFile.py/access?resId=1&materialId=0&confId=212501
>
> [5] ATLAS Weekly on HPC:
> https://indico.cern.ch/getFile.py/access?contribId=1&resId=1&materialId=slides&confId=282963
--
Facts aren't facts if they come from the wrong people. (Paul Krugman)
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