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  1. Lustre
  2. LU-10995

DoM2: allow MDT-only filesystems

Details

    • Improvement
    • Resolution: Unresolved
    • Minor
    • None
    • None
    • 9223372036854775807

    Description

      We don't yet support all-MDT systems, but I'm sure it is only a matter of time until we do. I think the main limitation is that we don't allow clients to use the filesystem until the MDS has connected to at least one OST, to prevent clients just getting errors when trying to use the filesystem (before DoM).

      We probably also need some testing to ensure we allow DoM file creates without OST components even if no OSTs are connected. We might also need to lift the 1GB dom_stripesize limit in that case.

      Finally, we might need to handle MDT and OST on the same node better during recovery, but it might also just work since the MDT always uses the same connection UUID.

      Attachments

        Issue Links

          is related to

          Improvement - An improvement or enhancement to an existing feature or task. LU-11425 Support quota for DoM

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Resolved
          is related to

          Epic - Created by Jira Software - do not edit or delete. Issue type for a big user story that needs to be broken down. LU-10176 Data-on-MDT phase II

          • Major - Major loss of function.
          • Open

          Bug - A problem which impairs or prevents the functions of the product. LU-11471 IO Errors during failover with very few number of OSTs

          • Minor - Minor loss of function, or other problem where easy workaround is present.
          • Closed

          New Feature - A new feature of the product, which has yet to be developed. LU-11023 OST Pool Quotas

          • Major - Major loss of function.
          • Resolved

          Technical task - A technical task. LU-11421 DoM: manual migration OST-MDT, MDT-MDT

          • Major - Major loss of function.
          • Resolved

          Activity

            [LU-10995] DoM2: allow MDT-only filesystems
            tappro Mikhail Pershin added a comment -

            Copied from LU-11471 to have all related notes in one ticket:

            With the advent of Data-on-MDT we will at some point want to allow filesystems with only MDTs to be created. At that point, this check has to be removed.

            As a starting point, we could add a tunable that allows this behavior to be selected by the admin - return an error if no OSTs are available, or cause the client to block and wait for an OST to become available. I think in the case where an OST was previously available, but they are temporarily offline due to failover, the client should block. If the file being created has a DoM component at the start, then it should not block.

            tappro Mikhail Pershin added a comment - Copied from LU-11471 to have all related notes in one ticket: With the advent of Data-on-MDT we will at some point want to allow filesystems with only MDTs to be created. At that point, this check has to be removed. As a starting point, we could add a tunable that allows this behavior to be selected by the admin - return an error if no OSTs are available, or cause the client to block and wait for an OST to become available. I think in the case where an OST was previously available, but they are temporarily offline due to failover, the client should block. If the file being created has a DoM component at the start, then it should not block.

            People

              wc-triage WC Triage
              adilger Andreas Dilger
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              Dates

                Created:
                Updated: