I would like to suggest that it would be great if it's possible to split backups into multiple parts during the backup process.

I know the option -s or --split but actually, it's just split the backup in the location into multiple parts but during the backup process the local storage is still in use. If you got a Server with 200GB space and 150 GB are used I can't Backup the server because the command "Plesk bin pleskbackup server --output-file=ftp://user:pass@destination/backup_file" would create one file with round 120 GB in local storage.

I would suggest an option that allows us to say "do a backup until you reach the 5 GB cap then transfer it, remove it from the local storage and start the next part".

Maybe I'm missing something here but I did a lot of research and didn't found a solution.

Sincerely,
Daniel Joos.

This helpdesk article has only negative reviews, which might imply that other users struggle with the same issue:
https://support.plesk.com/hc/en-us/articles/213391809-Backup-fails-with-error-Not-enough-free-disk-space-to-backup-selected-objects

Right now backing up to FTP means you need to have almost 50% disk space free. That means you can never use more than half the server storage you're paying for, otherwise you'll be unable to make a backup. Especially on AWS disk space is very expensive.

The issue exists because Plesk seems to utilize just plain zip commands with file split. Why not offer an additional backup method, where e.g. all Domains are backuped step-by-step / one-by-one to FTP?
E.g.
domain1.com -> domain1.zip
domain1.zip is uploaded to FTP
domain1.zip is deleted
continue with domain2.com

Or any other way to backup to FTP without the need to have almost 50% free disk space.

We have huge amounts of Backup Data (currently around 450gb per file). The whole process using FTP takes around ~ 13 hours to complete. Trying to restore something is a big bottleneck for us. Restoring from FTP is ****, and we searched for alternatives.

We decided to give SSHFS a try by mounting /var/lib/psa/dumps to the remote Server and disconfigured the FTP Settings. The result is annoying. The Backup now takes around 2,5 hours, the Plesk Backend is really fast now and local space is not consumed anymore!

So i suggest you to give SSHFS a try. It is like NFS but really easy. You can take a look at CURLFTPFS too! It can be used to mount external FTP Servers, but we decided to use SSHFS because of its simplicity...

It is easy to mount /var/lib/psa/dumps using the following command:

cat ~/.PASSWORDFORREMOTESERVER | sshfs -o passwordstdin,uid=id -u psaadm,gid=getent group psaadm | cut -d: -f3,Ciphers=arcfour,Compression=no,kernel_cache,workaround=rename USER@HOST:/DIRECTORY /var/lib/psa/dumps

You only have to store the password for the remote Server in an hidden file, e.g "/root/.backupserver" and pipe it to sshfs using the option -o passwordstdin. On the remote Server you have to enable the Ciphers arcfour in your sshd_config to make it work. This will make the whole connection faster.

After mounting the folder you can disable the FTP Settings in Plesk and therefor he writes to the local folder...

With using SSHFS the Backups are now created within 2,5 hours!

Give it a try! :-)