[pve-devel] qemu drive-mirror with zeroinit and ceph/rbd, not working

Wolfgang Bumiller w.bumiller at proxmox.com
Fri Jun 17 10:22:08 CEST 2016

> On June 17, 2016 at 10:01 AM Alexandre DERUMIER <aderumier at odiso.com> wrote:
> Hi,
> I have tested to drive-mirror an .raw file to ceph/rbd, with move disk feature,
> and it seem that the target rbd volume is full allocated.
> I'm not sure how is working the zeroinit patch ?

Currently it relies on qemu's use of bdrv_write_zeroes() and just skips that
while passing all other write requests through to the underlying block driver.
(It also tracks the target file's extents to deal with out-of-order writes,
such as zeroing a block which has previously been filled with data.)
It should be possible to change it to check the contents of all the regular
writes, too, but currently it doesn't do that. But if the .raw file isn't
fully allocated and the underlying file system supports SEEK_DATA/SEEK_HOLE
then it should work.

Added a reminder bugzilla entry: https://bugzilla.proxmox.com/show_bug.cgi?id=1032

> I'm seeing that it's enable in rbdplugin.
> Alexandre

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