Apple Xsan 1.4 - Manual (Page 185)

Glossary 185
label (verb) Used by some sources (such as ADIC) to refer to the process of preparing a
logical disk for use with a file system. In Xsan, however, use initialize 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 files,
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 physical disks.
LUN Logical unit number. A SCSI identifier for a logical storage device. 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 a metadata controller and exchanged over an Ethernet connection, while
actual file data is transferred over a Fibre Channel connection.
metadata controller The computer that manages metadata in an Xsan storage area
network.
mount (verb) In general, 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.
multipath method An Xsan storage pool property. Specifies how Xsan uses multiple
Fibre Channel paths between clients and storage. Can be set to static, which assigns
each LUN in a storage pool alternately to one of the connections when the volume is
mounted; or rotate, which alternates between the connections for higher performance.