[pve-devel] [PATCH 2/6] qemu_drive_mirror : handle multiple jobs

[Wolfgang Bumiller]

On Mon, Dec 19, 2016 at 07:05:58AM +0100, Alexandre DERUMIER wrote:
> >>AFAIR the patch looks already quite good. We currently prepare for 
> >>the 4.4 release, but when that is done we can start adding new features 
> >>like local disk live migration. 
> 
> Hi,
> Now that 4.4 has been release, could it be possible to apply live storage migration patches ?
> 
> I'll have some time until end of the year to polish them.

So far they've been working, but iirc there's still the issue where
breaking/failing connections _during_ the operation and/or the block
jobs failing to establish the connection in the first place go unnoticed
where we end up with possibly deleted disks instead of properly failing.
(Which is why I said I didn't like the tcp_ping check.)

IIRC that was the only blocker.

Basically the patchset has to work *without* tcp_ping() since it is an
unreliable check, and then we still have to catch failing connections
_correctly_. (There's no point in knowing that "some time in the past
you were able to connect to something which may or may not have been a
qemu nbd server", we need to know whether the drive-mirror job itself
was able to connect.)

> Also, I would like to improve them later, to add another feature, live migration to remote external proxmox cluster. (on different proxmox && storage).
> Vmware has this feature in entreprise premium, and I'll need it for some customers next year where I can't have downtime.

Sounds like a piece of work ;-)