[PVE-User] Storage Questions

Martin Maurer martin at proxmox.com
Thu Nov 25 19:00:39 CET 2010


> -----Original Message-----
> From: pve-user-bounces at pve.proxmox.com [mailto:pve-user-
> bounces at pve.proxmox.com] On Behalf Of Rakhesh Sasidharan
> Sent: Donnerstag, 25. November 2010 17:59
> To: pve-user at pve.proxmox.com
> Subject: [PVE-User] Storage Questions
> Hi,
> (Apologies if these questions are already documented anywhere. I had a
> quick look at the Proxmox documentation and forums but couldn't find
> anything.)
> I am a new user to Proxmox and KVM in general. Proxmox is excellent, my
> thanks to all those who created it. :)
[Martin Maurer] 
Thanks, you are welcome here.
> I have a couple of storage questions.
> 1) I note that its possible to add two types of local storage - as LVM or as a
> directory. Are there any advantages/ disadvantages to each? I have a second
> hard disk which I'd like to add to my storage pool and my initial thought was
> to initialize it via LVM, mount in a directory, and then add to Proxmox. But
> that's when I realized it can take the LVM group directly, so not sure if I
> should go that route or not.

[Martin Maurer] 
Use LVM for the second harddisk and use the block device for virtual disks. But this works only for KVM guests. See http://pve.proxmox.com/wiki/Storage_Model#LVM_Groups_with_Local_Backing
You have maximum performance as you are using block devices directly, no file system in between.

> 2) If I have a second hard disk, are there any performance advantages in
> moving the virtual machine disk to that machine instead of leaving them on
> the same disk as Proxmox? I remember reading somewhere (not KVM/
> Proxmox forums) that if the virtual machines disks are on a separate machine
> there is less competition between the host OS and the guests for the same
> disk ...
[Martin Maurer] 
Depends a bit on the storage controller but for modern hardware I see no difference.  Best is using block device directly (like described above), then raw format on the filesystem, qcow2 is the slowest.
Also think of using a SAN (FC, iSCSI, etc.).
> 3) If I have a virtual machine installed in a directory based storage, is there
> any easy way of moving the OS from that to an LVM storage?
[Martin Maurer] 
e.g. with backup/restore. Qmrestore allows to define the destination storage.
Br, martin
> Thanks,
> Rakhesh
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