[Bug 1911900] Re: [SRU] Active scrub blocks upmap balancer

Corey Bryant 1911900 at bugs.launchpad.net
Mon Feb 1 20:27:30 UTC 2021


Thanks very much Ponnuvel. I've pushed these changes to the groovy and
focal package branches. The builds are failing for unrelated 15.2.8
point release updates and I've asked Chris to take a look at those. Once
the package gets uploaded to groovy/focal we'll need to subscribe
ubuntu-sru to this bug.

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Title:
  [SRU] Active scrub blocks upmap balancer

Status in Ubuntu Cloud Archive:
  Invalid
Status in Ubuntu Cloud Archive ussuri series:
  Triaged
Status in ceph package in Ubuntu:
  Triaged
Status in ceph source package in Bionic:
  In Progress
Status in ceph source package in Focal:
  Triaged
Status in ceph source package in Groovy:
  Triaged
Status in ceph source package in Hirsute:
  Triaged

Bug description:
  [Impact]

  When scrubs are in progress, balancer stop due to the bug [0]. And
  shows:

  <timestamp> calc_pg_upmaps abort due to max <= 0

  in the logs.

  Typically when deep-scrub is done in maintenance windows and can take
  few hours. If balancing is paused for the duration, it can affect
  client I/O performance later when balacing starts happening after
  deep-scrub is done.

  This bug was introduced in Octopus. We need to backport upstream bug
  [0] to just Octopus. It's been fixed in upstream master branch [1].

  [Test Case]

  In an Octopus Ceph cluster that has some data (large enough to be able to notice balancing), take down one or more OSDs to introduce "unbalanced" objects.
  Make sure Ceph balancer module is enabled and active (which should be the default case in Octopus).
  Perform some I/O so that data goes to the rest of the OSDs.

  Then start deep-scrubbing and re-add the previously taken down so
  balancing start to happen.

  [Regression potential]

  Low potential. This is a bug fix of a previously correct code.

  If anything goes wrong, the balancer module might not function properly and thus
  leaving the cluster unbalanced and potentially requiring manual balancing.

  [Other Info]

  It's been accepted upstream and backported to Octopus. Ref [0] and
  [1].

  [0] https://tracker.ceph.com/issues/48309
  [1] https://github.com/ceph/ceph/pull/38337

  
  For Hirsute, James is working on a snapshot of Pacific and that should include the fix for this.

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