The file serve where all the homedir are stored is an NetApp Appliance, that include a lot of features. The 14 disks used by the device are configured in RAID 5 mode. The Server has 3 spare disk that are used whe one or more of the other disks stop working. The change is done automatically by the system and a mail message is sent to the System Administrators and to the technical support. The substitution of the damaged disk(s) is done without need to put offline the server.