vbd resize

vbd resize

[James Harper]

I'm investigating what would be required for a DomU's block device to be
resized (well... grown at least) without having to reboot the DomU.

Does the commercial product support this?

Thanks

James

Re: vbd resize

[Pasi Kärkkäinen]

On Thu, Jul 09, 2009 at 08:11:09PM +1000, James Harper wrote:
> I'm investigating what would be required for a DomU's block device to be
> resized (well... grown at least) without having to reboot the DomU.
> 
> Does the commercial product support this?
> 

This has been discussed here a couple of times, and it's also a feature
request for Xen 4.0.

I don't think it would be a lot of code to support this.. the upstream Linux
kernel already supports SCSI disk online resizing. Also RHEL 5.3 kernel supports
online SCSI disk resizing.

Earlier thread:
http://lists.xensource.com/archives/html/xen-devel/2008-09/msg00158.html

-- Pasi

Re: vbd resize

[Pasi Kärkkäinen]

On Thu, Jul 09, 2009 at 02:17:24PM +0300, Pasi Kärkkäinen wrote:
> On Thu, Jul 09, 2009 at 08:11:09PM +1000, James Harper wrote:
> > I'm investigating what would be required for a DomU's block device to be
> > resized (well... grown at least) without having to reboot the DomU.
> > 
> > Does the commercial product support this?
> > 
> 
> This has been discussed here a couple of times, and it's also a feature
> request for Xen 4.0.
> 
> I don't think it would be a lot of code to support this.. the upstream Linux
> kernel already supports SCSI disk online resizing. Also RHEL 5.3 kernel supports
> online SCSI disk resizing.
> 
> Earlier thread:
> http://lists.xensource.com/archives/html/xen-devel/2008-09/msg00158.html
> 

James: You might have enough knowledge of Xen internals to add support for
vbd resize to Xen hypervisor/tools :)

Then the next step would be to support it in domU kernels/drivers.

-- Pasi

Re: vbd resize

[James Harper]

> 
> I'm trying to add vbd resize to GPLPV, but it doesn't seem to work:
> 
> xm block-attach w2k3test32 phy:/dev/vg-xen/virt-test-0 hdb w
> 
> xenstore-read /local/domain/0/backend/vbd/377/832/sectors
> =44056576
> 
> lvextend --size=+1M /dev/vg-xen/virt-test-0
> 
> xenstore-read /local/domain/0/backend/vbd/377/832/sectors
> =44056576
> 
> The xenstore backend isn't updated to reflect the new size of the device... a
> strings | grep size of xen-blkback.ko module says:
> <6>xen-blkback:VBD Resize: Domid: %d, Device: (%d, %d)
> <6>xen-blkback:VBD Resize: new size %llu
> <4>xen-blkback:Error writing new size
> 
> So the code is definitely there, it's just not noticing that the device has been
> resize.
> 
> Any suggestions?
> 

My bad. I just checked the code and there actually has to be ring activity for the resize to be detected.

James

vbd resize

[James Harper]

I'm trying to add vbd resize to GPLPV, but it doesn't seem to work:

xm block-attach w2k3test32 phy:/dev/vg-xen/virt-test-0 hdb w

xenstore-read /local/domain/0/backend/vbd/377/832/sectors
=44056576

lvextend --size=+1M /dev/vg-xen/virt-test-0

xenstore-read /local/domain/0/backend/vbd/377/832/sectors
=44056576

The xenstore backend isn't updated to reflect the new size of the device... a strings | grep size of xen-blkback.ko module says:
<6>xen-blkback:VBD Resize: Domid: %d, Device: (%d, %d)
<6>xen-blkback:VBD Resize: new size %llu
<4>xen-blkback:Error writing new size

So the code is definitely there, it's just not noticing that the device has been resize.

Any suggestions?

Thanks

James