HP 4000.6000.8000 Enterprise Virtual Arrays - Manual (Page 174)

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 the
physical disks. If one of the data chunks becomes corrupted, the data can be reconstructed from
the parity chunk and the remaining data chunks.
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 Fibre Channel identifier consisting of a 16-character hexadecimal
number. A WWN is required for each Fibre Channel communication port.
174 Glossary