Servers typically use Direct-Attached Storage (DAS) disk drives for their storage, often (but not always) protected using RAID. As these disks fill up, additional capacity is needed--but adding that capacity can cause significant disruption to the business.

With DAS, servers need to be taken offline to allow new storage to be added. When existing disks are replaced, the server needs to be taken offline for many hours while data is copied from the old disks to new, larger disks. Typically, the copy is done at the file level and there is a risk that the copy may fail if there are open files.

iSCSI storage helps to solve these problems. By putting the storage on an Ethernet-based SAN, the storage can be virtualized and shared between servers.