How to report Storage capacity to the grid

https://savannah.cern.ch/task/?13702

Links:

• Castor Information provider (CIP) is at http://storage.esc.rl.ac.uk/grid-deployment/cip/
  • Drawbacks:
    • direct DB access (and may already have DB schema divergence in 2.9), some queries might be "expensive"
    • no source (and Lisp, i.e. hard to maintain ourselves even with source)
    • may not match our other reported data (from SLS and LEMON) → discussions with users
  • Advantage: "standard" tool, and somebody else is interfacing with the relevant WLCG working group..
• Miguel's Django thing at https://castorwebtools.cern.ch/SFS/diskspace/
  • bad:
    • Disk-only
    • might lag (run on demand, for now)
  • good:
    • consistent with SLS/LEMON
• directly pull data from SLS (i.e. the relevant dynamic update URL)
  • works for disk and Tape, would need a loop over VOs.
• GStat instance at CERN, pulls actual data from BDII (architecture). Knows about resource BDIIs, so as soon as we run some LDAP thing on the SRM headnodes our data should appear (might need to move this to CASTOR headnodes?)
• in previous times, LDIF was written by hand and came from CERN-CC-castorsrm-local-info