Xsan 2 Administrator Guide - Glossary

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file system A scheme for storing data on storage devices that allows applications to
read and write files without having to deal with lower-level details.
file system server See FSS.
An Xsan storage pool allocation strategy. In a volume consisting of more than one
storage pool, Xsan fills up the first pool before writing to the next.
format (verb) In general, to prepare a disk for use by a particular file 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 file 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 file 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 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 disk drives. See also physical disk.
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
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.
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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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.

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permissions for folders 74
read-only volumes 76
unmounting a volume 75

access control list. See ACLs

enabling and disabling 61
setting up in Xsan Admin 74

Active Directory 38, 42
adding clients to SAN 67
adding storage 20, 51

assigning to folder 57
described 17, 18
removing 58

affinity tag 17
allocation strategy

setting for volume 60

availability considerations 28



volume allocation strategy 60

block allocation size

choosing for a volume 60


client worker threads 71

adding 67
adding serial number 68
checking quotas from 83
defined 15
moving 69
removing from SAN 77
StorNext 106
using a volume 99

commands. See shell commands

with other versions of Xsan 10
with StorNext software 105

configuration files 122


adding 87
changing IP address 90
limit per SAN 20
listing hosted volumes 89
overview 15

cvadmin command 111
cvaffinity command 114
cvcp command 115
cvfsck command 116

checking volumes 64, 65
repairing volumes 66

cvlabel command 116
cvmkdir command 117
cvmkfile command 118
cvmkfs command 119
cvupdatefs command 119


defragmenting volumes 64
delay access time updates 71
directory cache size 71
directory services 24, 38, 42
Directory Utility 42


email notifications 97

configuring 40
guidelines 23

exclusive affinity tag 63

of affinity tag 63

expanding storage 20, 51
extended attributes

enabling 61


failover 88

forcing 88

failover priority 88
Fibre Channel

configuration requirements 22