Brocade Communications Systems StorageWorks 4400 Enterprise V User's Guide download pdf (Page 122)

UID Unit identification.

uninitialized

system

A state in which the storage system is not ready for use.

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.

Vdisk Virtual Disk. A simulated disk drive created by the controllers as storage for one

or more hosts. The virtual disk characteristics, chosen by the storage administrator,

provide a specific combination of capacity, availability, performance, and

accessibility. A controller pair simulates the characteristics of the virtual disk by

deploying the disk group from which the virtual disk was created.

The host computer sees the virtual disk as “real,” with the characteristics of an

identical physical disk.

See also active virtual disk, virtual disk copy, virtual disk family, and virtual disk

snapshot.

virtual disk See Vdisk.

virtual disk copy A clone or exact replica of another virtual disk at a particular point in time. Only

an active virtual disk can be copied. A copy immediately becomes the active

disk of its own virtual disk family.

See also active virtual disk, virtual disk family, and virtual disk snapshot .

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.

See also active virtual disk, virtual disk copy, and virtual disk snapshot.

virtual disk

snapshot

See snapshot.

Vraid0 A virtualization technique that provides no data protection. Data host is broken

down into chunks and distributed on the disks comprising the disk group from

which the virtual disk was created. Reading and writing to a Vraid0 virtual disk

is very fast and makes the fullest use of the available storage, but there is no

data protection (redundancy) unless there is parity.

Vraid1 A virtualization technique that provides the highest level of data protection. All

data blocks are mirrored or written twice on separate physical disks. For read

requests, the block can be read from either disk, which can increase performance.

Mirroring takes the most storage space because twice the storage capacity must

be allocated for a given amount of data.

Vraid5 A virtualization technique that uses parity striping to provide moderate data

protection. Parity is a data protection mechanism for a striped virtual disk. A

striped virtual disk is one where the data to and from the host is broken down

into chunks and distributed on the physical disks comprising the disk group in

which the virtual disk was created. If the striped virtual disk has parity, another

chunk (a parity chunk) is calculated from the set of data chunks and written to

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