Apple has introduced a RAID card designed specifically for the Xserve. The add-on includes 256MB of RAID cache and supports hardware RAID levels 0, 1, and 5. Apple claims it can deliver up to 198MB per second throughput when using RAID 5. It also does not use a PCI Express expansion slot, and includes a built-in battery that protects the RAID cache for up to 72-hours. Even without the card, you can still use the software RAID utility built in to Mac OS X Server to stripe two or three internal drives into a RAID 0 array to increase performance or create a RAID 1 array for data protection against a drive failure. The Xserve RAID card replaces the built-in SATA/SAS controller board. To order the card with an Xserve, you must choose either all SATA or SAS drives in drive bays 1 through 3. The RAID card is priced at $999 and is available as a built-to-order option from the online Apple Store.