One backup mode for both (qemu & lxc)

[Sessa45]

Hello everybody,

Currently I am faced with the question why I can secure with Proxmox with the "snapshot" mode both qemu and on lxc? As I understand it, apply two types of backup methods for the two types of virtualization?

Source: https://pve.proxmox.com/wiki/Backup_and_Restore

Regards

 

[Sessa45]

Any idea here?

 

[tom]

Any idea here?

I do not get your question.?

 

[Sessa45]

Oh well. The documentation states that there are 3 modes for VM and 3 for LXC. Why exactly can I use the modes that are intended for LXC, also with KVM?

I do not understand the meaning / difference between the modes.

Spoiler: Backup VM

Backup modes for VMs:
stop mode
This mode provides the highest consistency of the backup, at the cost of a short downtime in the VM operation. It works by executing an orderly shutdown of the VM, and then runs a background Qemu process to backup the VM data. After the backup is started, the VM goes to full operation mode if it was previously running. Consistency is guaranteed by using the live backup feature.

suspend mode
This mode is provided for compatibility reason, and suspends the VM before calling the snapshot mode. Since suspending the VM results in a longer downtime and does not necessarily improve the data consistency, the use of the snapshot mode is recommended instead.

snapshot mode
This mode provides the lowest operation downtime, at the cost of a small inconstancy risk. It works by performing a Proxmox VE live backup, in which data blocks are copied while the VM is running. If the guest agent is enabled (agent: 1) and running, it calls guest-fsfreeze-freeze and guest-fsfreeze-thaw to improve consistency.

Spoiler: Backup LXC

Backup modes for Containers:
stop mode
Stop the container for the duration of the backup. This potentially results in a very long downtime.

suspend mode
This mode uses rsync to copy the container data to a temporary location (see option --tmpdir). Then the container is suspended and a second rsync copies changed files. After that, the container is started (resumed) again. This results in minimal downtime, but needs additional space to hold the container copy.

When the container is on a local file system and the target storage of the backup is an NFS/CIFS server, you should set --tmpdir to reside on a local file system too, as this will result in a many fold performance improvement. Use of a local tmpdir is also required if you want to backup a local container using ACLs in suspend mode if the backup storage is an NFS server.

snapshot mode
This mode uses the snapshotting facilities of the underlying storage. First, the container will be suspended to ensure data consistency. A temporary snapshot of the container’s volumes will be made and the snapshot content will be archived in a tar file. Finally, the temporary snapshot is deleted again.

 

[Alwin]

I do not understand the meaning / difference between the modes.

The names and general outcome of the modes are the same but they do not quite do the same operations to achieve them. Read the text of each mode carefully, you will spot the differences.