[Openstack-operators] Experience with Cinder volumes as root disks?

Chris Friesen chris.friesen at windriver.com
Tue Aug 1 21:23:41 UTC 2017

On 08/01/2017 02:32 PM, Mike Lowe wrote:
> Two things, first info does not show how much disk is used du does.  Second, the
> semantics count, copy is different than clone and flatten.  Clone and flatten
> which should happen if you have things working correctly is much faster than
> copy.  If you are using copy then you may be limited by the number of management
> ops in flight, this is a setting for more recent versions of ceph.  I don’t know
> if copy skips zero byte objects but clone and flatten certainly do.  You need to
> be sure that you have the proper settings in nova.conf for discard/unmap as well
> as using hw_scsi_model=virtio-scsi and hw_disk_bus=scsi in the image properties.
>   Once discard is working and you have the qemu guest agent running in your
> instances you can force them to do a fstrim to reclaim space as an additional
> benefit.

Just a heads-up...with virtio-scsi there is a bug where you cannot boot from 
volume and then attach another volume.

(The bug is 1702999, though it's possible the fix for 1686116 will address it in 
which case it'd be fixed in pike.)


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