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ALICE Computing Meeting August 2 2007 [message #4808] Thu, 02 August 2007 13:34
Kilian Schwarz is currently offline  Kilian Schwarz
Messages: 91
Registered: June 2004
Location: GSI, Darmstadt
continuous participant
From: *
recommendation: no directories should be created manually. Let xrootd create necessary subdirectories during the copy process. Otherwise, if one has to create directories manually one should make sure that the user "xroot" has permission to write !!!

- how to delete files in the xrd cluster ?
* one trusted person should have the task and the right to delete files on the cluster
* a cron job running on the file servers removes files automatically following input from a list of files in a text file. This list should be exposed via web so that everybody has a chance to intervene. The actual deleting task shall be done 1 time per week. Eventually the files should be moved beforehand to a temporary file space where they will lie for 1 more week before being deleted.
* every ALICE user can delete files by his/her own by using Marians xrd tool. This tool will work by using lsf methods and a user is supposed to be able to delete only files in the own namespace (to be included in the xrd tool). For this the user "xroot" must be part of the group "alice".

- transfer CERN GSI
maximum speed reached 7.5 MB/s which corresponds to roughly half the bandwidth of GSI. We can go up to 75% but Mathias Muench has to be informed beforehand. The maximum transfer speed can not be kept on continuous basis so far since there is a bug in xrdcp which creates stalled processes with a certain probability. They have to be killed via cron job. So far 50% of the requested files have been transferred. The list of transfered files is attached.

- PROOF tutorial
everything went fine except that on 2 nodes the memory was overused and they died consequently. Reason for this was also the uneven distribution of data files which concentrated on those 2 nodes. Marian implemented the creation of random samples only in TDSet, not in TChain.
Solution: more swap space for WNs. All of them will get 32 GB of swap space. When the swap space is touched MonaLisa will send automatic warning message to ALICE.
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