HP StorageWorks HP-UX Kit V3.0B for Enterprise Virtual Array Installation and Configuration Guide (AA-RUHKB-TE, October 2003)

Glossary
47HP-UX Kit V3.0B for Enterprise Virtual Array Installation and Configuration Guide
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
whose 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.
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 because 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.