[pve-devel] savevm tests

Alexandre DERUMIER aderumier at odiso.com
Fri Aug 31 10:16:58 CEST 2012


>>I think we can simply call an external helper for such storage types. Will dig deeper 
>>into qemu code now. 

Ok thanks ! (you have more skill than me, I'm not sure I can help ;)

I thing I didn't have check, is where the vmstate is stored if we have mutiples devices.
On the first disk ? on the boot disk ?

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

De: "Dietmar Maurer" <dietmar at proxmox.com> 
À: "Alexandre DERUMIER" <aderumier at odiso.com> 
Cc: pve-devel at pve.proxmox.com 
Envoyé: Vendredi 31 Août 2012 10:09:10 
Objet: RE: [pve-devel] savevm tests 

> >>Why not possible? We can simply allocate a normal volume, and store 
> state there? 
> 
> I want to say, without hacking qemu code ;) But maybe it's possible, but is 
> really difficult. 

looks easy to me ;-) I am just exploring the savevm.c code - will send more 
details later. 

> It need to code a nexenta block driver for qemu (forking libiscsi), and a 
> volume management to do space,save the vmstate,... 
> Seem really difficult to do, and maintain in time 

No, I guess there will be a simpler solutions. 

> >>We have VM which use qcow2, sheepdog, rdb and nexenta at the same 
> time. How should that work? 
> yes indeed, 
> But I really don't think that users will mix all the storage on same vm. (and 
> have enough money to build and maintain all the storage clusters ;) But, if 
> they really want to do it, 

They will mix, I am 100% sure about that ;-) 

> I see 2 kinds of storages for snapshots: 
> 
> - qemu "internal" storage, using qemu block drivers. 
> - qcow2 
> - rbd 
> - sheepdog 
> 
> 
> 
> - external storage 
> like -nexenta, 
> and maybe other futur storage like: 
> -lvm (dm-thinp, for local snapshot by exemple) 
> - why not btrfs in the future 
> -netapp storage(I say that because I'm planning to build a big big netapp 
> cluster for a customer in the coming months) 
> -... 
> 
> 
> qemu internal storage, must have same features (missing rbd vmstate, but it 
> should come soon). 
> They also have the same snapshots/rollback capabilities. (multi branch tree, 
> read/write snapshots) So we can mix them on the same vm, and use 
> snapshots. 
> But we can't mix them with other storages. (savevm exit if it detect a storage 
> without savevm capability, like raw file,blockdevice,iscsi device) 
> 
> 
> external storage: 
> they maybe have not the same snapshots capabilities, no vmstate. 
> So theses storage could not be mixed with other storages, if we want to use 
> snapshot. 
> 
> 
> We just need to check the differents mixed storage used by the vm before 
> allow the snapshots. 
> 
> What do you think ? 

I think we can simply call an external helper for such storage types. Will dig deeper 
into qemu code now. 

- Dietmar 



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Alexandre D e rumier 

Ingénieur Systèmes et Réseaux 


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