[openstack-dev] [OpenStack][Nova]May be performance issues of connect_volume in Nova

Joe Gordon joe.gordon0 at gmail.com
Tue Aug 26 17:11:45 UTC 2014

On Tue, Aug 26, 2014 at 5:36 AM, Wang Shen <ws1210 at gmail.com> wrote:

> Hi, All
> I have done some work to test the performance of LUN scanning, use
> "iscsiadm" with "--rescan" like what Nova dose. In my test, a host
> connected with a lot of LUNs , more than 1000 LUNs. Because "--rescan"
> will cause kernel to scan all of the LUNs connected to the host, it
> costs several minutes to complete the scanning.
> According to "connect_volume" at line 284 in nova.virt.libvirt.volume.py:
> https://github.com/openstack/nova/blob/master/nova/virt/libvirt/volume.py#L252
> Nova uses "iscsiadm" with "--rescan" to detect new volume, but this
> command will scan all of the LUNs, including all the others which
> already connected to this host. So if a host has a large number of
> LUNs connected to it, the connect_volume will be very slow.
> I think connect_volume needn't scan all of the LUNs, only need scan
> the LUN specified by connection_info.
> Is it necessary to discuss a more efficient way to improve this issues.

It sounds like this is a bug; we use https://bugs.launchpad.net/nova to
track bugs so they don't get lost.

> --
> Best wishes
> ======================  Peter.W  ======================
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> OpenStack-dev at lists.openstack.org
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