HP StorageWorks 6000 HP StorageWorks 6000-series Virtual Library System User G - Page 344

data restore To recover data files stored on virtual or physical media. data retention period The length of time data is retained (stored) on virtual or physical media. 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 backup Typically refers to backing up data on disks rather than on tape. Disk-to-disk 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 backup Archiving in which data is initially copied to backup storage on a disk-based storage system, such as a VLS, and then periodically copied again to a tape storage system. See also data migration. dynamic disk filesystem A finely-tuned filesystem developed to handle large block I/O typical of a streaming backup/restore environment. This filesystem is optimized for sequential access and very large file sizes. echo copy extent 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.) 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 when the primary component becomes unavailable through either failure or scheduled down time. 344 Glossary