Best practices for data backup¶

When a virtual machine is deleted, the data saved on the machine will be deleted too. As we can not guarantee that a virtual machine and therefore the data on the machine will be accessable at all times due to possible hardware or software errors, we collect some best practices for data backup here.

Remote backup¶

Although it is a rare occurence, it is possible that even volumes and snapshots might vanish or get corrupted. Therefore the absolute best practice for backuping data is by copying it to a remote hard drive, disk or other storage solution which is not part of the de.NBI Cloud.
You may find a tutorial on how to copy data from your machine to a local or remote storage here.
If you have access to an object storage, please refer to the documentation of your object storage.

Backup with volumes¶

How to attach/mount volumes

You may find more information on how to create, attach and mount volumes here.

Volumes are a great way to backup files as they persist independently of your virtual machines (i.e. a mounted volume will not be deleted if your virtual machine is deleted) and the size limit is only determined by your requested project volume storage.

When to backup with volumes

Backup data on a volume when you want to backup data often, backup data from different virtual machines or want to restore data without booting a new virtual machine. Backups on a volume are also independend of the state of your system, i.e. they are stored safely even if you accidentally corrupt your system.

There are different ways to backup data on a volume:

Backup manually.
Mount the volume to the virtual machine you want to backup data from and either copy it with
```
cp -a /path/to/files/to/backup /path/to/backupDirectory/on/mounted/volume
```
or use a program like rsync to sync data between two directories.
Another good practice is to archive the files you want to backup, e.g.
```
tar -zcf /path/to/backupDirectory/on/mounted/volume/backup.tgz /path/to/files/to/archive
```
Backup automatically.
Mount the volume to the virtual machine you want to backup data from and create a cron job to automatically transfer files to your mounted backup directory, e.g.
```
0 0 * * * cp -a /path/to/files/to/backup /path/to/backupDirectory/on/mounted/volume 
```
or
```
0 0 * * * tar -zcf /path/to/backupDirectory/on/mounted/volume/backup.tgz /path/to/files/to/archive
```
This cron jobs will backup your files every day at midnight.
For a more detailed guide on how to create and use cron jobs, please refer to one of the many guides you may find on the internet.

To transfer the backuped data to another machine B you will need to mount the volume on the machine B (and detach and unmount it first if it is still attached to machine A).

A drawback of volumes is that they may only be mounted to one virtual machine at a time, which means that you can not backup data of multiple machines in parallel on one volume. One way to remedy this is by setting the volume up as a NFSv4 Share. A guide on how to do this is out of the scope of this guide and may be found for example here.

Backup with snapshots¶

How to create and use snapshots

You may find more information on how to create and start snapshots here.

Snapshots preserve the files on the root disk and the full state of your RAM and you may use a snapshot to boot a new virtual machine. Snapshots may only be created manually and can not be automated for users of a SimpleVM project.

When to backup with snapshots

Backup data with a snapshot when you want to preserve the full state of your virtual machine (e.g. before deleting your virtual machine) or want to boot up one or many virtual machine(s) with your data already present.

Drawbacks to consider

As a snapshot preserves the full state of your virtual machine, only snapshots up to a maximum of 256 GB RAM are supported!
Snapshots are only available when creating a new virtual machine, they are not suitable to restore data on a running machine!
Data on ephemeral disks will not be saved, data on ephemeral disks will be lost when not saved on a different storage solution, e.g. a volume!
Data on attached and mounted volumes will not be saved in a Snapshot, but are of course still available on your volume.