[LU-4640] Last unlink should trigger HSM remove by default

• Type: Bug
• Resolution: Fixed
• Priority: Minor
• Fix Version/s: Lustre 2.10.0
• Affects Version/s: Lustre 2.5.0
• Labels: HSM patch
• Severity: 3
• Assignee: Bruno Faccini (Inactive)
• Reporter: Aurelien Degremont (Inactive)

Description

In current code, when an archived file is removed from the file system, no HSM request is triggered. We rely on Changelogs and RobinHood reading them to have it sending corresponding hsm_remove requests to clean those orphans in HSM backend. This is done in purpose, to provide a way to implement "soft unlink". RobinHood will remove the file in the backend after a grace time. During this time, Admins could restore the file from the HSM if they want to (using import feature).

Requiring a RobinHood setup to handle this cleaning is a too big limitation. We should consider modifying this behaviour.

By default, Lustre should automatically add a HSM_REMOVE request for any last unlink. This way, no file will be leaked in the archive.
A tunable should be added to disable this behaviour (should we add this to hsm_policy?) and go back to a mode where an external component is responsible for tracking UNLINK changelogs and add hsm_remove requests when needed (Robinhood) (current behaviour).

Issue Links

• is related to: LU-9654 fix problem of Remove Archive on Last Unlink policy
• is related to: LU-7881 sanity-hsm test_26b: @@@@@@ FAIL: Copytool should have stopped