Apple Xsan 1.0 - Manual (Page 42)

42 Glossary
initialize In general, to prepare a disk for use by a particular file system. In Xsan, to
prepare a LUN for use in a storage pool.
label (noun) An identifying name for a LUN.
label (verb) StorNext File System term for initializing a LUN. See “initialize.”
LUN SCSI logical unit number. In Xsan, an unformatted logical storage device such as
an Xserve RAID array or slice.
metadata Information about a file system and the files it stores (for example, which
disk blocks a file occupies or which blocks are available for use). In Xsan, metadata is
managed by controllers but stored on SAN volumes. Xsan clients and controllers
exchange metadata over an Ethernet connection to avoid interfering with file data,
which is transferred over a Fibre Channel connection.
metadata controller The computer that manages Xsan metadata. What StorNext File
System calls a file system server (FSS).
mount (verb) To cause an Xsan volume to appear on a client’s desktop like any other
local disk. Xsan volumes are mounted and unmounted on clients by the controller, not
by clients themselves.
multipath method An Xsan storage pool property. Specifies how Xsan utilizes multiple
Fibre Channel paths between clients and storage. Can be set to rotate, which alternates
each read or write between available paths for higher performance, or static, which
assigns each LUN in a volume alternately to a path at mount time.
RAID array A group of physical disks organized and protected by a RAID scheme and
presented by hardware or software as a single logical disk. In Xsan, RAID arrays appear
as LUNs that are combined to form storage pools.
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
storage 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 of 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 Xsan stripes user data. Storage pools are combined
to form Xsan volumes.
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