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[Tim Bell <1509304@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

QCOW2 performance can be significantly improved by setting the l2-cache-
size parameter for large qcow2 based storage (such as images and
ephemeral drives) (see
https://events.linuxfoundation.org/sites/events/files/slides/p0.pp_.pdf).

Adding support for this optional parameter (which adds [...]-drive
file=hd.qcow2,l2-cache-size=2097152 to the qemu CLI) would allow
operators and/or users to configure a more tuned configuration.

A simple simple implementation where a default value could be set in
nova.conf would already give an improved flexibility. Ideally, this
could also be specified as an image or flavor property so that only
large drives would need to allocate the additional memory.

I could not locate an option such as this in the OpenStack versions up
to Liberty.

** Affects: nova
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1509304

Title:
  l2-cache-size support for drives

Status in OpenStack Compute (nova):
  New

Bug description:
  QCOW2 performance can be significantly improved by setting the l2
  -cache-size parameter for large qcow2 based storage (such as images
  and ephemeral drives) (see
  https://events.linuxfoundation.org/sites/events/files/slides/p0.pp_.pdf).

  Adding support for this optional parameter (which adds [...]-drive
  file=hd.qcow2,l2-cache-size=2097152 to the qemu CLI) would allow
  operators and/or users to configure a more tuned configuration.

  A simple simple implementation where a default value could be set in
  nova.conf would already give an improved flexibility. Ideally, this
  could also be specified as an image or flavor property so that only
  large drives would need to allocate the additional memory.

  I could not locate an option such as this in the OpenStack versions up
  to Liberty.

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