HP 6400/8400 HP StorageWorks 6400/8400 Enterprise Virtual Array User Guide - 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 uninitialized system UNRECOVERABLE Condition unwritten cached data UPS UUID Unit identification. A state in which the storage system is not ready for use. An EMU condition that occurs when one or more elements in the drive enclosure have failed and 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. Also known as unflushed data. See also dirty data. 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. 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 virtual disk family Vraid0 Vraid1 Vraid5 Vraid6 Variable disk capacity that is defined and managed by the array controller and presentable to hosts as a disk. 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. Optimized for I/O speed and efficient use of physical disk space, but provides no data redundancy. Optimized for data redundancy and I/O speed, but uses the most physical disk space. Provides a balance of data redundancy, I/O speed, and efficient use of physical disk space. Offers the features of Vraid5 while providing more protection for an additional drive failure, but uses additional physical disk space. W World Wide Name write back caching write caching WWN See WWN. 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. 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. World Wide Name. A unique identifier assigned to a Fibre Channel device. 142 Glossary