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[Kalle Happonen <kalle.happonen@xxxxxx>]

Public bug reported:

Setup:
CentOS 6 + RDO Icehouse (code seems to be the same in trunk)

When doing a nova migrate, the actual backing disk file is copied over with rsync. I assume the code came from this report
https://bugs.launchpad.net/nova/+bug/1025259

The rsync code uses the "-z" flag for compression. This is probably fine
for cases with lightly used disks. However, with a disk full of content,
it gets very slow. Rsync is not multithreaded so with a single E5-2670v2
core, we get ~12MB/s transfer speed (CPU bound). With the modest
compression that is achieved this is significantly slower than no
compression.

If possible, some speed test should be done without compression for disk
files with different content. There might not be a reason to use
compression here at all.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1478800

Title:
  Libvirt migrations with rsync are slow

Status in OpenStack Compute (nova):
  New

Bug description:
  Setup:
  CentOS 6 + RDO Icehouse (code seems to be the same in trunk)

  When doing a nova migrate, the actual backing disk file is copied over with rsync. I assume the code came from this report
  https://bugs.launchpad.net/nova/+bug/1025259

  The rsync code uses the "-z" flag for compression. This is probably
  fine for cases with lightly used disks. However, with a disk full of
  content, it gets very slow. Rsync is not multithreaded so with a
  single E5-2670v2 core, we get ~12MB/s transfer speed (CPU bound). With
  the modest compression that is achieved this is significantly slower
  than no compression.

  If possible, some speed test should be done without compression for
  disk files with different content. There might not be a reason to use
  compression here at all.

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