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Documentation #17978

Wrong diskcache parameter name for OpenStack Havana and Icehouse

Added by Michael Eischer 11 months ago. Updated 8 months ago.

Status:
Resolved
Priority:
Normal
Assignee:
-
Target version:
-
Start date:
11/21/2016
Due date:
% Done:

0%

Tags:
Backport:
Reviewed:
Affected Versions:
Release:

Description

I've been investigating some performance issues I've encountered on an OpenStack Icehouse deployment. The configuration closely resembles the one from http://docs.ceph.com/docs/master/rbd/rbd-openstack/.
However, libvirt was using "none" as disk cache mode despite the configuration line in nova.conf:

libvirt_disk_cachemodes="network=writeback"

A closer examination revealed that the correct configuration would have been:

disk_cachemodes="network=writeback"

Due to an unknown reason there is no deprecated_name with a libvirt prefix for the disk_cachemodes configuration option (see https://github.com/angdraug/nova/blob/rbd-ephemeral-clone-stable-icehouse/nova/virt/libvirt/driver.py#L252). This holds for both OpenStack Havana and Icehouse. It is possible at least for Icehouse to use the configuration for Juno, which (implicitly) fixes the wrong parameter name.

Associated revisions

Revision 877245e6 (diff)
Added by Michael Eischer 8 months ago

doc: Fixes parameter name in rbd configuration on openstack havana/icehouse

The documentation for using rbd together with openstack havana/icehouse
states that the parameter libvirt_disk_cachemodes should be added to
the nova.conf file. However, this is the only parameter that has no
legacy name with a 'libvirt_' prefix. (See
https://github.com/openstack/nova/blob/icehouse-eol/nova/virt/libvirt/driver.py#L252
for the configuration option)
Thus the configured disk_cachemodes were not applied, defaulting to
no caching.

Fixes: #17978
Signed-off-by: Michael Eischer <>

History

#1 Updated by Michael Eischer 9 months ago

Ping Any progress on this?

#2 Updated by Nathan Cutler 9 months ago

@Michael: Can you open a PR at https://github.com/ceph/ceph with your proposed fix? The documentation is under doc/

#3 Updated by Jason Dillaman 9 months ago

@Michael: note that Icehouse and Havana are both EOLed by the upstream community. Does this issue apply to Grizzly+ releases of OpenStack as well?

#4 Updated by Michael Eischer 8 months ago

I've opened a pull request: https://github.com/ceph/ceph/pull/13403

@Jason: The documentation fix doesn't apply to OpenStack Juno or later which have their own documentation section(s). OpenStack Grizzly is not covered by the rbd documentation, but also doesn't seem to have the 'libvirt_' prefix for disk_cachemodes.

#5 Updated by Jason Dillaman 8 months ago

  • Status changed from New to Resolved

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