Apple Discontinues the Xserve RAID and instead promotes The Promise VTrak E-Class RAID Subsystem. Apple also introduced Xsan 2 which has the following features.
Xsan allows you to consolidate data into a single storage volume that’s accessible to all systems on the storage area network (SAN). Adding capacity is as easy as attaching more RAID storage systems to your Fibre Channel network.
Fibre Channel network
The SAN volume connects to the Xsan metadata controller and all Xsan clients through a high-speed Fibre Channel switch. Apple has qualified many popular third-party switches for use with Xsan.
Xsan metadata controller
Xsan includes software called the “metadata controller,” which acts as the traffic cop for the SAN. When an Xsan client attempts to read or write to a file, it gets permission from the metadata controller, then accesses the data directly on the SAN over high-speed Fibre Channel. Any Xserve or Mac Pro running Mac OS X Server can be an Xsan metadata controller.
Mac desktop or Xserve systems running Xsan have direct block-level access to files stored on the SAN volume and full read/write capability. As performance needs grow, Xsan allows you to add servers and computers to the SAN. With Xsan, one SAN can handle hundreds of clients.
File system metadata is handled “out of band” over a private Ethernet network shared by all systems connected directly to the SAN. This frees up Fibre Channel bandwidth for high-performance storage throughput.
An Xserve with Mac OS X Server and Xsan can share data from the SAN volume with an unlimited number of networked computers over the Ethernet network using file-sharing protocols, such as AFP, SMB/CIFS, and NFS.