Re: [libvirt] [PATCH 0/6] Support online block resizing

On Thu, Sep 01, 2011 at 02:14:23PM +0100, Daniel P. Berrange wrote: > On Wed, Aug 31, 2011 at 09:31:58PM +0800, Osier Yang wrote: >> Upstream QEMU introduced online block resizing to resize the >> block device when domain is running since commit 6d4a2b3a4795. >> It simply reuses existing "bdrv_truncate" method which is used >> by "qemu-img" to resize the images. This means it supports to >> resize all the format that "qemu-img resize" supports. E.g. >> qcow2, raw, qed, qcow, etc. (NB, it doesn't support to shrink >> size of qcow2 image, and QEMU reports "An undefined error >> has ocurred" in this case). >> >> For block device of virtio bus, the guest can update the device >> size automatically, needs kernel support, since kernel-2.6.32-117: >> >> http://patchwork.usersys.redhat.com/patch/33040/ >> >> For block device of SCSI bus, one needs to execute command like >> below in the guest (linux) to update the size: >> >> % echo> /sys/class/scsi_device/0:0:0:0/device/rescan >> >> For block device of IDE bus, seems there is no way to let guest >> update the size after resizing. > Your API proprosal looks reasonable, but unfortunately the QEMU > command 'block_resize' is either broken, or incomplete since it > does not have a way to notify the guest that a block device has > been resized, independantly of actually resizing the host file. > This is required in order for guest disk resize to work on LVM, > SCSI, iSCSI, etc block devices, since QEMU cannot itself do a > resize of the block devices. The resize has to be done either > by libvirt using host commands, or by the SAN administrator on > the remote storage appliance. > > IMHO, we should not commit to the libvirt API design, until we > can get confirmation from QEMU about whether they will fix the > block_resize command to work for block devices, or add a new > command for just notifying guests of external block device > resizes See this thread... http://lists.nongnu.org/archive/html/qemu-devel/2011-09/msg00068.html Daniel