Restore only blocks changed after last backup

[Esa Riikonen]

Hi for some reason I have got an idea:
With Proxmox Backup Server working with PVE server I can restore VM as only blocks changed after last backup are transferred over lan.

But testing restore VM always copy all actual used blocks in vm disk
vm having 40GB disk (tested now with directory xfs/qcow2 and VLM thin. just LVM not tested yet).
There is about 15GB actual windows data.

1. firts backup: about 15GB data transferred a
2. second snapshot backup: few megabyte data transferred

3. restore this vm without removing original vm: 15GB data transferred
->not only few megabytes I hope

With small about datadisk this is not a problem but larges this may take a time.

The root reason asking this: Is Backup/Restore possible to use as missing snapshot feature with sentral SAN storage LVM disks
Looks Liverestore also restores the whole disk from backup.

Esa

 

[dakralex]

Hello Esa!

If I have understood you correctly, you have created two backups of a virtual machine with Proxmox Backup Server and then restored said VM to the first backup, is that correct? If so, then the behavior is as expected, as restoring a VM means that you want to get back a specific state of the VM at one point of time (e.g. for disaster recovery). That is, restoring a VM is used to e.g. recover from a disk failure from a hard drive and therefore you usually want to rewrite the whole disk image in case of corruption.

The incremental backups, however, work by getting a list of the most recent backed up chunks of the VM on the PBS and then sending only the chunks that were modified since the last backup (when dirty block bitmaps are used). This works only on sequential backups and not in reverse.

Cheers,
Daniel

 

[Esa Riikonen]

So, restore works like most backup software hadles it. Full restore always.
Thanks for respondig

 

[jlauro]

Probably not exactly what you are looking for, but maybe one of the following will help you plan your backup and dr setup:

You can do zfs replication from one proxmox server to another to get a more incremental transfer. Not a substitute for backups, but can give you an incremental restore point on the remote side. That said, don't think replication works to LVM, and zfs on iSCSI can't be shared live on multiple nodes, but could be use for incremental clones that you could then snapshot...

Also PBS to PBS is incremental. A restore is still a full restore, but if part of your goal is point in time backups available over slower links without doing a full transfer over the slow link, multiple PBS servers will also give you that.

 

[waltar]

Just for information as with the basic lvm cmd's just snapshot block replication updates is possible. Who is interessed in there might take a look into eg. this script for more comfortable usage https://github.com/mpalmer/lvmsync .