Big manual backup block server.sh "long" time
Is a growing problem because webs goes bigger and bigger.. and if /var/backup is not so fast (HDD or NFS..) than a big > 50GB Web could take a long time to run while the server.sh is blocked for other things.
Simplest solution would be another cron for backup tasks but this bring the race conditions problem with parallel task (backup is running and someone delete the web in this time ...)