Am 02.04.25 um 10:30 schrieb Wolfgang Bumiller:
On Tue, Apr 01, 2025 at 08:21:30PM +0200, Thomas Lamprecht wrote:
This sounds pretty inefficient - especially when
comparing with qmrestore's ability to just read read from stdin.
The reading from stdin is quite limited, does not support sparse files
efficiently, and does not support our live-restore feature.
If we can *pull* data out-of-order from the backup provider via a better
protocol (like NBD which Thomas mentioned), holes in the disks don't
need to be transferred over the network, and we could probably support
live-restore, where the VMs immediately start running *during* the
restore process. (qemu would simply treat read-requests from the guest
which have not yet been restored with a higher priority while otherwise
continuing to copy the data in-order in the background)
Neither pulling nor out-of-order is an option in the Bareos architecture.
Some alternatives btw. are providing a fuse or ublk device on the PVE
side which pulls data from bareos (or to which bareos can push data
which, like qemu's "fleecing" mode, could store the not-yet restored
portions in temporary files, discarding them as they are read by/moved
to qemu).
That's basically like staging the image just that you can start reading
before we finish writing. I'll keep it in mind, even tough I don't think
it is really feasible.
*Technically* we could have a mode where we allocate the disks and "map"
them onto the system (potentially via nbd, or `rbd map` for ceph etc.)
Yes, please do.
*But* it would make live-restore impossible with that plugin.
There will be no live-restore with Bareos.
If we would ever consider implementing this, on the Bareos side it would
be pretty complicated and full of limitations. In that case we would
probably just implement yet another plugin for PVE.
Which is why the most flexible thing to do is to use a `qemu-img` call
and giving it the paths, or more precisely, the URLs to the disks.
I understand how this makes sense. However, if you don't have the data
in a format that qemu-img can consume, things become complicated.
Best Regards,
Andreas
--
Andreas Rogge andreas.ro...@bareos.com
Bareos GmbH & Co. KG Phone: +49 221-630693-86
http://www.bareos.com
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