And this.
Chris.
On 05/07/2018, 14:59, "GRIDPP2: Deployment and support of SRM and local storage management on behalf of Chris Brew - UKRI STFC" <[log in to unmask] on behalf of [log in to unmask]> wrote:
HI Sam,
Slide 4: Oxford, Glasgow, QMUL, RHUL and Bristol are storageless for CMS and use IC, RAL PPD and Brunel for Storage (UK Xrootd redirector in front of those sites). CMS software is aware of this and routes jobs requesting data on any of the storage sites to that site plus the storageless sites, measured efficiency at the satellite site is not noticeably below that of the parent.
Slide 10: CAVEAT: This is for CMS AAA data, most data is still read from the local storage, this is only for remote reads. Attached are some plots for a pair of xrootd proxies, one disk caching (figure 1) one memory caching (figure 2) for the same 24 hour time period. Note Disk cache is file caching, memory cache is block caching.
Top Plot in each figure shows the caching factor (log10(Tx/Rx)) +ve good, -ve bad, bottom plot is simple Rx (red, left vertical scale) and Tx (green, right vertical scale) in bytes.
Conclusion: File caching disk proxies for CMS AAA data are pants.
I had hoped to have comparable results for a block caching disk proxy, but I’ve never managed to get it to run for 24hrs.
If you’ve got access to Jupyter, are any good with mathplotlib, and want to clean up the plots I can send you a copy of the notebook.
Slide 13
Disk + CPU Sites with satellite CPU only sites work for CMS as long as the job placement is aware and the CPU only sites are near enough in network terms (whole UK seems to be near enough – Glasgow reading from IC, RALPP + Brunel
Sorry to dump all this on you after you’ve written you slides, feel free to include or discard as you please
From: "[log in to unmask] UK" <[log in to unmask]> on behalf of Sam Skipsey <[log in to unmask]>
Reply-To: Sam Skipsey <[log in to unmask]>
Date: Thursday, 5 July 2018 at 13:33
To: "[log in to unmask] UK" <[log in to unmask]>
Subject: A draft of the CHEP Tier 2 talk
As promised, here's a draft of the CHEP Tier 2 caching talk.
All comments gratefully received (the frontspiece needs me to add credits anyway, so if you comment you get a credit as well)...
Sam
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