"552 Disk full" - or "please upload later" - or "server is running out of disk space" - or "error 28 from storage engine" - or errors like that - are at the server level, indicating that the shared data storage (SAN) partition(s) are full or nearly full or a server read/write-file type of error - which is preventing you from uploading files - or using cPanel - or your site from using a MySQL database - or your script from starting a session
this is a server issue so Admins will need to fix it - your files (data) are NOT the problem and there is nothing you can do but wait
This problem is due to a full system replication occurring for our backup archives. Unfortunately the backup has the temporary side effect of higher than normal disk utilization to store file system block changes in a copy-on-write partition snapshot. Let us know if you see the problem return, it is something we have to fix from our end until the backup is completed.