Backup fails in SolusVM 2: make sure directory exists: sftp: "Failure" (SSH_FX_FAILURE)

Symptoms 

SVM_ERROR: cannot backup the virtual server "1bdc0b5c-d287-43de-a30d-37d350a27362": back up disk "sda" with path "/var/lib/libvirt/images/251/5900ae55ce2690d4861c255ea48f4af8": upload failed, backup is corrupted: make sure directory exists: sftp: "Failure" (SSH_FX_FAILURE)

Cause

Issues on the backup node

Resolution

Make sure:

1. Connection is possible from CR to Backup node
2. There is enough disk space on Backup node
3. It is possible to create files and directories in the backup directory