HP StorageWorks 6400/8400 - Enterprise Virtual Array User Manual page 145

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
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
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
virtual disk See snapshot.
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.
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.
active virtual disk, virtual disk
active virtual disk, virtual disk
active virtual disk, virtual disk
HP StorageWorks 6400/8400 Enterprise Virtual Array user guide
copy, virtual disk family, and
family, and virtual disk snapshot
copy, and virtual disk snapshot.
virtual disk
.
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