Behind the scenes: CISL using SAM plus HPSS to enforce allocation limits

The High Performance Storage System (HPSS), which CISL uses to manage its tape archive, doesn’t have a built-in way to enforce quotas, so the CISL Systems Accounting Manager (SAM) supports that new feature. HPSS reports summary weekly storage holdings to SAM by user and project, then SAM reports to HPSS which projects have overspent their allocations. HPSS accounting happens only once a week, so users should be aware of when changes actually take effect.

For example, a user whose storage allocation is overspent might delete enough files on a Thursday or Friday to be under the allocation limit, but the weekly HPSS accounting run is done each Sunday. Changes in the project’s HPSS holdings then are updated in SAM on Monday. At that point, the system recognizes that the allocation is no longer overspent and it restores the user’s ability to write files to HPSS. The actual tape capacity that was freed up is reclaimed later on.

Requests for occasional short-term (one week) exceptions to allocation limit enforcement to compensate for the accounting time delay should be sent to for consideration.