proxmox snapshot vs xen/vmware snapshot

i still cant figure out if i'm doing it wrong or if this is some kind of limitation of proxmox.

on xen/vmware, i simply right click on vm -> take snapshot, and within seconds i have a backup i can revert back to or clone off of at any time.

on proxmox, when i create snapshot, the bigger the vm the longer it takes, on average they take roughly 10 minutes for 100gb+ vms. i have done all kinds, qcow2/lvm/separate storage/etc for backups, so i believe i did everything right.

it looks like proxmox creates FULL compressed backup files of the vm. i'm not sure what xen/vwmare uses but it tends to take less space and a lot faster.

so my question is, is proxmox's snapshot slower (and different) than xen/vmware's?
 
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m.ardito

Active Member
Feb 17, 2010
1,473
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38
Torino, Italy
are you sure you're not doing a "snapshot backup" ?

pve can do "snapshot backup", ie: it takes an lvm snapshot and then use that to do a full backup, freeing the vm immediately while doing backup.

only kvm vm with qcow2 disks can also take snapshots, which take seconds, and you can delete them revert to previous, etc.

Marco
 
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NdK73

Member
Jul 19, 2012
69
3
8
Bologna, Italy
www.csshl.net
You're taking a backup, not a snapshot. At least if you did it on a VM backed by LVM: the GUI won't allow you to take snapshots!
On LVM, you have to use "lvcreate -s" if the VM uses a single disk, or "qm suspend" + "lvcreate -s" (for every disk) + "qm resume" (shouldn't take more than 1sec).
Remember that LVM snapshots have some limitations. The most important are that they impact performances and are not cluster-safe (unless there's exactly *one* vm using that disk and you take the snapshot on the host where that VM is running -- I think that's the reason the GUI doesn't implement it).
And a snapshot is not a backup...
 

mo_

Member
Oct 27, 2011
399
3
18
Germany
theres actually a difference. When you create a snapshot, you create a CoW-image of the original image, meaning that any changes to the disk after this point will be saved to the new image, allowing you to go back to the original image (which also becomes read-only ("immutable") when creating a snapshot). You can take these sorts of snapshots with most of the storage options available to proxmox (namely RBD, LVM, as well as with qcow2-images on any file-based storage).

However, when you use backup in pve, it not only creates this snapshot, it also creates a backup of the snapshot (the now consistant file/state) which obviously has to write all the data of the disk to your backup location.

PS: I wrote this, while NdK73's response wasnt there yet, my post seems a little redundant now but oh well
 
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Thanks for the replies.
FYI, I am mainly doing openvz containers.
I guess this is why I am confused because only KVM supports the live snapshots.
Is it safe to assume that due to the nature of openvz, live snapshots are not possible (ram state)?
If so, i'm curious to see how Xen handle this differently, because even with their paravirtualization it can handle live snapshots.
 

mo_

Member
Oct 27, 2011
399
3
18
Germany
as far as I know the openvz guys are currently developing CRIU to be able to handle snapshotting not only for containers but for individual processes as well. It's still in development though, so I am merely giving you a heads up.

What you can do to at least get filesystem snapshots of openvz containers is use a filesystem that allows for snapshotting. Like ZFS (which is stable) or btrfs (which might be stable in 10 years or so) or cephfs (should be stable around Q4 this year, if they can keep their schedule).
 
as far as I know the openvz guys are currently developing CRIU to be able to handle snapshotting not only for containers but for individual processes as well. It's still in development though, so I am merely giving you a heads up.

What you can do to at least get filesystem snapshots of openvz containers is use a filesystem that allows for snapshotting. Like ZFS (which is stable) or btrfs (which might be stable in 10 years or so) or cephfs (should be stable around Q4 this year, if they can keep their schedule).

Doesn't LVM support snapshotting too? What is the difference between it and zfs in terms of snapshots?
 

acidrop

Member
Jul 17, 2012
194
4
18
I do not know how xen handle snapshots but zfs snapshots have been ultra fast for me.
 

blackpaw

Member
Nov 1, 2013
230
2
18
If you disable using ssh for kvm snapshots it's a lot faster. Can' remember how its done though.
Sent from my RM-977_1008 using Tapatalk
 

blackpaw

Member
Nov 1, 2013
230
2
18
Possibly, I thought it was used for snapshot creation as well.
Sent from my RM-977_1008 using Tapatalk
 

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