Both features mentioned in the title, play a special role and are very important when data center grows up, when new switches, hosts and virtual machines are needed. They allow us to expand SAN infrastructure (fabric) and not spend additional money by the way.
Backup is the keyword in case of data storage. Even the newest technologies deployed will not work out if one day turns out that some hard drives with crucial data don’t work, RAID may failed owing to the numbers of broken hard disks, your SAN has been destroyed or data have been accidentally (or not) permamently…