HP StorageWorks 12000 - Virtual Library System EVA Gateway User Manual page 254

data restore To recover data files stored on virtual or physical media.
data retention The length of time data is retained (stored) on virtual or physical media.
period
deduplication After a backup application completes writing to disk, the backup data is
processed in the background on the virtual cartridges and then any duplicate
data is eliminated. This reduces the amount of disk space required because the
backup drives no longer need to hold multiple versions of the same backup data.
disk array Two or more hard drives combined as a single logical unit for increased capacity,
speed, and/or fault-tolerant operation. Disk arrays are logically grouped into a
storage pool.
See also storage pool.
disk mirroring A technique in which data is written to two duplicate disks simultaneously.
Mirroring provides data protection in the case of disk failure, because data is
constantly updated to both disks. Using this technique, if one of the hard drives
fails the system can instantly switch to the other disk without any loss of data or
service.
See also RAID 1-level data storage and failover protection.
disk striping The process of dividing a body of data into blocks and spreading the data blocks
across several partitions on several disks.
See also RAID.
disk-to-disk Typically refers to backing up data on disks rather than on tape. Disk-to-disk
backup backup systems provide a very fast single file restore capability compared with
disk-to-tape backup.
See also data restore and virtual tape.
disk-to-disk-to-tape Archiving in which data is initially copied to backup storage on a disk-based
backup storage system, such as a VLS, and then periodically copied again to a tape
storage system.
See also data migration.
dual port virtual Virtual devices (for example, the two host or device ports on each FC card in
devices the node) with connectivity to two ports so that the device can be connected to
more than one input or output.
dynamic disk A finely-tuned filesystem developed to handle large block I/O typical of a
filesystem streaming backup/restore environment. This filesystem is optimized for sequential
access and very large file sizes.
echo copy A feature within automigration that automatically synchronizes the physical
cartridges to matching virtual cartridges (with the same barcodes) based on
user-defined policies, and is totally transparent to the backup application. (Echo
copy is similar to mirror copy.)
extent The minimum amount of disk space allocated for writing by the VLS dynamic
disk filesystem. A smaller extent reduces wasted disk space, but decreases restore
performance. The VLS extent size is 32MB.
See also data restore.
failover protection A backup operational mode in which the functions of a system component (such
as a hard drive or power supply) are assumed by secondary system components
254 Glossary