Specifications

316 Glossary
QTSS QuickTime Streaming Server. A technology that lets you deliver media over the
Internet in real time.
queue An orderly waiting area where items wait for some type of attention from the
system. See also print queue.
QuickTime Streaming Server See QTSS.
RADIUS Remote Authentication Dial-In User Service.
RADIUS server A computer on the network that provides a centralized database of
authentication information for computers on the network.
RAID Redundant Array of Independent (or Inexpensive) Disks. A grouping of multiple
physical hard disks into a disk array, which either provides high-speed access to stored
data, mirrors the data so that it can be rebuilt in case of disk failure, or both. The RAID
array is presented to the storage system as a single logical storage unit. See also RAID
array, RAID level.
RAID 0 A RAID scheme in which data is distributed evenly in stripes across an array of
drives. RAID 0 increases the speed of data transfer, but provides no data protection.
RAID 0+1 A combination of RAID 0 and RAID 1. This RAID scheme is created by striping
data across multiple pairs of mirrored drives.
RAID 1 A RAID scheme that creates a pair of mirrored drives with identical copies of
the same data. It provides a high level of data availability.
RAID 10 A hybrid RAID level that uses software RAID striping to stripe data across RAID
1 (or mirrored) arrays.
RAID 3 A RAID scheme that stripes data across two or more drives and stores parity
data on a dedicated drive. In the event of a disk failure, the redundant parity bits can
be used to reconstruct data on any drive.
RAID 30 A hybrid RAID level that uses software RAID striping to stripe data across RAID
3 arrays.
RAID 5 A RAID scheme that distributes both data and parity information across an
array of drives one block at a time, with each drive operating independently. This
enables maximum read performance when accessing large files.
RAID 50 A hybrid RAID level that uses software RAID striping across RAID 5 arrays.
RAID array A group of physical disks organized and protected by a RAID scheme and
presented by RAID hardware or software as a single logical disk. In Xsan, RAID arrays
appear as LUNs, which are combined to form storage pools.