The CTA Tape Lifecycle

Introduction

In CTA, each tape information is stored in the CTA Catalogue and are managed by the mean of cta-admin command.

Different tape states and supported state transitions

What can be done on each final state

State	Queue user read requests	Queue user write requests	Queue repack requests	Queue repack read sub-requests (*)	Queue repack write sub-request(*)	Mountable	Reclaimable
ACTIVE	YES	YES	NO	NO	YES	YES	YES
DISABLED	YES	YES	NO	NO	YES	NO	YES
REPACKING	NO	NO	YES	YES	NO	YES	NO
REPACKING_DISABLED	NO	NO	YES	YES	NO	NO	NO
BROKEN	NO	NO	NO	NO	NO	NO	YES
EXPORTED	NO	NO	NO	NO	NO	NO	NO

(*) Repack sub-request queueing is handled internally by the maintenance process.

Tape states explained

• ACTIVE:
  • A tape that is ACTIVE is a tape that is in good condition to allow a user to read data from it or to write data to it. A newly added tape to CTA will be ACTIVE by default.
• DISABLED:
  • A tape that is DISABLED cannot be mounted, but can still have retrieve requests queued to it.
  • Can be set for the following reasons:
    • A tape server disabled it after encountering some issue that lead to failure (example: failed dismount).
    • Monitoring probes decided to disable it (too many errors over the past XX hours,...).
    • An operator think the tape is in bad shape and must be kept away from users while it is investigated.
  • A tape should not stay in this state for more than 1 week, person on rota to follow up on tapes disabled for longer than one week.
• REPACKING:
  • A tape should be moved to REPACKING state before the operator submits a repack request. Otherwise, the repack request won't be accepted.
  • Likewise, it's not possible to move out of REPACKING while a repack request is ongoing (except for the REPACKING_DISABLED state).
  • When a change to REPACKING is requested, the tape will first move to the temporary state REPACKING_PENDING. Then, it waits for the maintenance process to clean all user requests on the tape queue, before finally moving it to REPACKING state. For more details see: Queue Cleanup Runner.
• REPACKING_DISABLED:
  • The state REPACKING_DISABLED is similar to DISABLED, but for repacking tapes (we can't move out of repacking states while a repack is ongoing).
  • A tape should not stay in this state for more than 1 week, person on rota to follow up on tapes disabled for longer than one week.
  • New repack requests can be queued on a REPACKING_DISABLED tape. However, no tape will be mounted while it's on this state.
• BROKEN:
  • A tape can stay in this state for long and it is very likely that it is its very last state.
  • When a change to BROKEN is requested, the tape will first move to the temporary state BROKEN_PENDING. Then, it waits for the maintenance process to clean all user requests on the tape queue, before finally moving it to BROKEN state. This guarantees that all requests are properly disposed of.
  • Can be set for the following reasons:
    • A problematic (earlier DISABLED) tape that requires non-trivial efforts for its data to be recovered:
      • low level slow tape extract is needed
      • sent for data recovery to the vendor = the tape is not present in the library
      • all recovery attempts exhausted, the tape is permanently broken but experiment action is needed (delete the lost files from the catalogs)
    • In rare cases an ACTIVE tape that fall on the floor because of a gripper incident can move from ACTIVE straight to BROKEN as it must be physically put back in a slot.
  • Normally, very few tapes are in the BROKEN state.
  • No operations are allowed for a BROKEN tape.
• EXPORTED:
  • A tape can stay in this state for long. It means that the tape was removed from the tape library.
  • While we at CERN we do not remove tape cartridges from tape libraries, other sites do. Therefore, the EXPORTED state should help to distinguish that.
  • This state would behave very similarly to BROKEN state. The difference is on the error messages reported to the user.