[PVE-User] Storage migration issue with thin provisionning SAN storage

[Alexandre DERUMIER]

Hi,
the limitation come from nfs. (proxmox use correctly detect-zeroes, but nfs protocol have limitations, I think it'll be fixed in nfs 4.2)

I have same problem when I migrate from nfs to ceph.

I'm using discard/triming to retrieve space after migration.

----- Mail original -----
De: "Dhaussy Alexandre" <ADhaussy at voyages-sncf.com>
À: "proxmoxve" <pve-user at pve.proxmox.com>
Envoyé: Mardi 4 Octobre 2016 10:34:07
Objet: Re: [PVE-User] Storage migration issue with thin provisionning SAN storage

Hello Brian, 

Thanks for the tip, it may be my last chance solution.. 

Fortunatly i kept all original disk files on a NFS share, so i 'm able 
to rollback and re-do the migration...if manage to make qemu mirroring 
work with sparse vmdks.. 


Le 03/10/2016 à 21:11, Brian :: a écrit : 
> Hi Alexandre, 
> 
> If guests are linux you could try use the scsi driver with discard enabled 
> 
> fstrim -v / then may make the unused space free on the underlying FS then. 
> 
> I don't use LVM but this certainly works with other types of storage.. 
> 
> 
> 
> 
> 
> On Mon, Oct 3, 2016 at 5:14 PM, Dhaussy Alexandre 
> <ADhaussy at voyages-sncf.com> wrote: 
>> Hello, 
>> 
>> I'm actually migrating more than 1000 Vms from VMware to proxmox, but i'm hitting a major issue with storage migrations.. 
>> Actually i'm migrating from datastores VMFS to NFS on VMWare, then from NFS to LVM on Proxmox. 
>> 
>> LVMs on Proxmox are on top thin provisionned (FC SAN) LUNs. 
>> Thin provisionning works fine on Proxmox newly created VMs. 
>> 
>> But, i just discovered that when using qm move_disk to migrate from NFS to LVM, it actually allocates all blocks of data ! 
>> It's a huge problem for me and clearly a nogo... as the SAN storage arrays are filling up very quickly ! 
>> 
>> After further investigations, in qemu & proxmox... I found in proxmox code that qemu_drive_mirror is called with those arguments : 
>> 
>> (In /usr/share/perl5/PVE/QemuServer.pm) 
>> 
>> 5640 sub qemu_drive_mirror { 
>> ....... 
>> 5654 my $opts = { timeout => 10, device => "drive-$drive", mode => "existing", sync => "full", target => $qemu_target }; 
>> 
>> If i'm not wrong, Qemu supports "detect-zeroes" flag for mirroring block targets, but proxmox does not use it. 
>> Is there any reason why this flag is not enabled during qemu drive mirroring ?? 
>> 
>> Cheers, 
>> Alexandre. 
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