HP 6400/8400 User Manual page 142

transceiver The device that converts electrical signals to optical signals at the point where the fiber cables
connect to the fibre channel elements such as hubs, controllers, or adapters.
U
UID Unit identification.
uninitialized A state in which the storage system is not ready for use.
system
UNRECOVERABLE An EMU condition that occurs when one or more elements in the drive enclosure have failed and
Condition have disabled the enclosure. The enclosure may not be able to recover or bypass the failure; this
will require repairs to correct the condition. This is the highest-level condition. It takes precedence
over all other errors and requires immediate corrective action.
unwritten cached Also known as unflushed data.
data See also dirty data.
UPS Uninterruptible power supply. A battery-operated power supply guaranteed to provide power to
an electrical device in the event of an unexpected interruption to the primary power supply.
Uninterruptible power supplies are usually rated by the amount of voltage supplied and the length
of time the voltage is supplied.
UUID Unique universal identifier. A unique 128-bit identifier for each component of an array. UUIDs
are internal system values that users cannot modify.
V
virtual disk Variable disk capacity that is defined and managed by the array controller and presentable to
hosts as a disk.
virtual disk family A virtual disk and its snapshot, if a snapshot exists, constitute a family. The original virtual disk
is called the active disk. When you first create a virtual disk family, the only member is the active
disk.
Vraid0 Optimized for I/O speed and efficient use of physical disk space, but provides no data
redundancy.
Vraid1 Optimized for data redundancy and I/O speed, but uses the most physical disk space.
Vraid5 Provides a balance of data redundancy, I/O speed, and efficient use of physical disk space.
Vraid6 Offers the features of Vraid5 while providing more protection for an additional drive failure, but
uses additional physical disk space.
W
World Wide Name See WWN.
write back caching A controller process that notifies the host that the write operation is complete when the data is
written to the cache. This occurs before transferring the data to the disk. Write back caching
improves response time since the write operation completes as soon as the data reaches the
cache. As soon as possible after caching the data, the controller then writes the data to the disk
drives.
write caching A process when the host sends a write request to the controller, and the controller places the data
in the controller cache module. As soon as possible, the controller transfers the data to the physical
disk drives.
WWN World Wide Name. A unique identifier assigned to a Fibre Channel device.
142 Glossary