HP 12000 User Manual page 196

inputs/outputs per A performance measurement for a host-attached storage device or RAID controller.
second
L
library A storage device that handles multiple units of media and provides one or more drives for reading
and writing them, such as a physical tape library and virtual tape library. Software emulation of
a physical tape library is called a virtual tape library.
See also virtual tape library..
logical unit number An address used in the SCSI protocol to access a device within a target. In the case of the VLS,
(LUN) a LUN is assigned to each virtual library and tape drive.
LUN mapping A mechanism of changing the LUN assignments for a specific host.
LUN masking An authorization process that makes a LUN available to some hosts and unavailable to other
hosts.
M
mean time until The average time until a component failure can be expected to cause data loss. This includes the
data loss (MTDL) consideration that RAID redundancy can protect against data loss from the failure of a single
component.
media access A low-level unique hardware identifier for every Ethernet port in the world that is physically stored
control (MAC) inside a network card or similar network interface. MAC addresses are assigned by the IEEE.
address
media server A computer whose purpose is to move or copy data from one location to another, such as from
network clients to tape cartridges in a library.
metadata The data in the first sectors of a disk drive that the system uses to identify virtual disk members.
mirroring The act of creating an exact copy or image of data.
N
node A server that contains the hardware and firmware required to run a virtual library system. This
refers to a hardware assembly containing a power supply, cooling fans, motherboard, expansion
boards, and internal hard drives to support the VLS system.
O
oversubscription A condition that exists when more virtual media storage is configured on a VLS than there is
physical storage available.
Because the VLS dynamically allocates storage space as user data is written, the VLS allows you
to allocate more storage for virtual media than is physically available.
P
port mapping A mechanism of assigning a LUN (virtual device), such as a virtual library or tape drive, to a
specific FC host port. Port mapping allows you to load-balance the LUNs among the FC host ports
to maximize bandwidth.
At this time, you must manually load-balance the virtual tape drives in a VLS.
primary node A computer (node) that provides primary administrating and control for backup and restore
operations on a server cluster and provides communication and control for all secondary servers
on the system.
R
RAID A RAID volume consists of more than one drive, but appears to the operating system to be a
single logical disk. RAID improves performance by disk striping, which involves partitioning each
drive's storage space into units. By placing data on multiple disks, I/O operations can overlap
in a balanced way, improving performance.
196 Glossary