[pve-devel] Storage migration: online design solution

[Alexandre DERUMIER]

> 
> target can be file or device, (So I think it's for migrate between 2 storages available on same host) 
> 
>>Yes, and this is were NBD comes into play. 


Maybe I'm wrong, but I don't think we need nbd for storage migrate on the same host. (just use new device/file as target option of qmp mirror)


>>Why do you think that? Late us say a VM has to disk devices on server-x 
>>and server-y. If you then migrate storage from server-x to server-z 
>>where should VM then be running? I have not seen any anything 
>>indicating drive-mirror should be followed by a VM migrate.
start ndb server on remote server
Launch drive-mirror on remote nbd, 
at the end of block mirror,the vm run on source server with remote storage on target server through nbd socket
the migrate vm to the target server
then rattach the target volume to the vm (drive-reopen (?))
stop nbdserver

This is the way is implemented in libvirt

	




----- Mail original ----- 

De: "Michael Rasmussen" <mir at datanom.net> 
À: pve-devel at pve.proxmox.com 
Envoyé: Mercredi 9 Janvier 2013 07:44:46 
Objet: Re: [pve-devel] Storage migration: online design solution 

On Wed, 09 Jan 2013 03:49:21 +0100 (CET) 
Alexandre DERUMIER <aderumier at odiso.com> wrote: 

> 
> target can be file or device, (So I think it's for migrate between 2 storages available on same host) 
> 
Yes, and this is were NBD comes into play. 

> 
> So, if you use ndb server as target, is it for migrate storage between 2 differents host ? (From 1 local storage on 1 host to another local storage on different host by example) 
> 
In principle NBD can be running on a remote server or local but I would 
guess using NBD for a local device must be slower than writing directly 
to the device. 
> If yes, I think we need to migrate also the vm on the new host ? 
Why do you think that? Late us say a VM has to disk devices on server-x 
and server-y. If you then migrate storage from server-x to server-z 
where should VM then be running? I have not seen any anything 
indicating drive-mirror should be followed by a VM migrate. 


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