Apple Xsan 2 (Third Edition) - Manual (Page 125)

Glossary 125
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 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 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 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.
RAID level A storage allocation scheme used for storing data on a RAID array.
Specified by a number, as in RAID 3 or RAID 0+1.
RAID set See RAID array.
round robin An Xsan storage pool allocation strategy. In a volume consisting of more
than one storage pool, Xsan allocates space for successive writes to each available
pool in turn.
SAN Storage area network. In general, a network whose primary purpose is the
transfer of data between computer systems and storage elements and among storage
elements. In Xsan, a SAN is a combination or one or more controllers, storage volumes,
and storage clients.
storage pool A group of logical disks that share common characteristics, such as
throughput or latency, across which user data is striped. In Xsan, storage pools are
combined into volumes. The StorNext File System calls this a stripe group.
stripe (verb) To write data to successive stripes in a RAID array or LUN.
stripe breadth An Xsan storage pool property. The number of bytes of data, expressed
as a number of file system blocks, that Xsan writes to a LUN in a storage pool before
moving to the next LUN in the pool.
stripe group The StorNext File System term for an Xsan storage pool.
volume A mountable allocation of storage that behaves, from the client’s perspective,
like a local hard disk, hard disk partition, or network volume. In Xsan, a volume consists
of one or more storage pools. See also logical disk.