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Modifications to eos `evict`/`stagerrm` command

As discussed in #269 (closed), we want to do the following improvements to the EOS command stagerrm:

1. Remove the evict counting logic out of stagerrm code (see code), into the prepare evict code.

  • Means prepare -e will have the opposite counter logic of prepare -s, which makes sense.
  • As a result, stagerrm will always delete the file (for the multiple replica case, see bellow). It can be freely called by an operator, or by prepare -e when the evict counter reaches zero.
  • stagerrm does not increment/decrement the evict counter.
  • stagerrm simply drops the evict counter when called. Except if there are other disk replicas still alive.
  • Done

EDIT: See comment #278 (comment 6857102).

2. Always force the stagerrm deletion on the MGM:

  • If the FST fails to delete the file, this will result in dark data. This is a known and acceptable disadvantage.
  • Done

3. Add an optional parameter --fsid <fsid> to the eos stagerrm command, to define which disk replica to remove:

  • Parameter option:
    • File system ID (recommended by Elvin - value accepted by _dropstripe(...))
  • The FST fst-gcd should pass this parameter to stagerrm.
  • Not passing the parameter will mean that all replicas should deleted.
  • If no more replicas remain, the evict counter should also be dropped.
  • stagerrm won't delete a replica without tape copy (as done now):
    • What if there is no tape copy but 2+ disk copies?
      • R: This would be a weird scenario. Better not to allow any stagerrm (partial or not) if there is not a tape replica.
  • If there are other replicas still alive, the evict counter should be preserved.
  • Done

4. Replace EOS stagerrm command by evict:

  • As discussed in #277 (closed), stagerrm s an artifact from the CASTOR era, whose behaviour is now different on CTA.
  • Therefore, we decided to replace it by evict.
  • The usage of stagerrm should be removed gradually. At first we will keep both, but then remove stagerrm once all the the tools have been testes against evict.
  • Done

Corresponding EOS Jira issue:

Edited by Joao Afonso