Apple Xsan User Manual download pdf (Page 124)

12 4 Glossary

le system A scheme for storing data on storage devices that allows applications to

read and write les without having to deal with lower-level details.

le system server See FSS.

ll An Xsan storage pool allocation strategy. In a volume consisting of more than one

storage pool, Xsan lls up the rst pool before writing to the next.

format (verb) In general, to prepare a disk for use by a particular le system.

FSS File system server. The StorNext File System term for the computer that manages

metadata in a storage area network (SAN). In Xsan, this is called a metadata controller.

initialize To prepare a disk for use by a particular le system. In Xsan, to prepare a

RAID array for use in a storage pool.

label (noun) In Xsan, an identifying name for a LUN. You can assign a label to a LUN

before or during setup of an Xsan storage pool.

label (verb) Used by some sources (such as StorNext) to refer to the process of

preparing a logical disk for use with a le system. In Xsan, however, initialize is used to

refer to preparing a disk for use in a storage pool.

logical disk A storage device that appears to a user as a single disk for storing les,

even though it might actually consist of more than one physical disk drive. An Xsan

volume, for example, is a logical disk that behaves like a single disk even though it

consists of multiple storage pools that are, in turn, made up of multiple LUNs, each of

which contains multiple disk drives. See also physical disk.

LUN Logical unit number. A SCSI identier for a logical storage device. In Xsan, an

unformatted logical storage device such as an Xserve RAID array or slice.

metadata Information about a le system and the les it stores (for example, which

disk blocks a le occupies or which blocks are available for use). In Xsan, metadata is

managed by a metadata controller and exchanged over an Ethernet connection, while

actual le data is transferred over a Fibre Channel connection.

metadata controller The computer that manages metadata in an Xsan storage area

network.

mount (verb) To make a remote directory or volume available for access on a local

system. In Xsan, to cause an Xsan volume to appear on a client’s desktop, just like a

local disk.

physical disk An actual, mechanical disk. Compare with logical disk.

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.

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Apple Xsan User Manual Page 124