yahoo-eng-team team mailing list archive

[Gorka Eguileor <2023079@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

When doing a live volume migration (block migration) thin volumes
effectively become thick because all bytes are copies from the source to
the destination.

I understand that only the filesystem can know about the block that are
unallocated, but Nova can set the "detect_zeroes" when doing the block
mirroring.

This doesn't seem to work for all drivers, but I have confirmed that it
works for NFS and RBD volumes.  Probably someone more knowledgeable
should look into why it doesn't work for iSCSI and such.

It requires some additional CPU computational power, so we shouldn't be
setting it for normal operations, but I believe the big difference in
time and network bandwidth during live migration is well worth it.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/2023079

Title:
  Sparseness is not preserved on live migration

Status in OpenStack Compute (nova):
  New

Bug description:
  When doing a live volume migration (block migration) thin volumes
  effectively become thick because all bytes are copies from the source
  to the destination.

  I understand that only the filesystem can know about the block that
  are unallocated, but Nova can set the "detect_zeroes" when doing the
  block mirroring.

  This doesn't seem to work for all drivers, but I have confirmed that
  it works for NFS and RBD volumes.  Probably someone more knowledgeable
  should look into why it doesn't work for iSCSI and such.

  It requires some additional CPU computational power, so we shouldn't
  be setting it for normal operations, but I believe the big difference
  in time and network bandwidth during live migration is well worth it.

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