Space tokens situation at sites

Space tokens situation at sites after the migration to new space tokens configuration happened in March-April 2011

This is a survey on the deployment of space tokens at LHCb sites and the space occupancy, site by site, after the migration to the new space tokens configuration. The script ( dirac-dms-check-STs.py ) used to check the space usage according to LFC and to SRM had to be changed after the space tokens migration. A new script is ready, which does the following operations:

  • queries the DIRAC StorageUsage service to get the usage for each DIRAC storage element as reported by LFC
  • queries the SRM to get the space usage of each space token

compare the space usage LFC-SRM in the following way:

For LHCb_USER there is a 1-1 correspondence between the DIRAC SE and the SRM space token. It's straightforward.

For LHCb-Tape: it is impossible to compare, because SRM interface provides the usage of disk space only, and not of the used space on tape. So we can't compare with the LFC!

For LHCb-Disk: in principle it should be: space of LHCb-Disk = sum( space of disk SEs, i.e. for site X, X-DST, X_M-DST, X-FAILOVER, X_MC_M-DST, X_MC-DST). But currently, this is NOT the case, because the old space tokens (2010 space tokens) still contain some data. This data will be eventually removed, but probably it will take months. Given this situation, to get the total usage according to SRM, should sum: LHCb-Disk + the old disk space tokens (the LHCb_M-DST, LHCb_DST, LHCb_MC_M-DST, LHCb_MC_DST, LHCb_FAILOVER ). Actually, this doesn't work either, sometimes because the SRM doesn't expose any more the old space tokens, and some other times because, even if they are exposed and the used space can be retrieved, the sum of the space does not match the usage reported by LFC. In order to have a complete accounting of the used space at sites, LHCb needs to get a dump of the storage elements on a periodic basis (e.g. one a week). This will allow to perform consistency checks, and also to have a precise accounting of the used space at each site.

Site by site

See here a review site by site to clarify the current situation.

-- ElisaLanciotti - 18-Jul-2011

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Topic revision: r4 - 2011-10-07 - unknown
 
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