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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. This way 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-
Archiving in which data is initially copied to backup storage on a disk-based
tape 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
filesystem
a streaming backup/restore environment. This filesystem is optimized for
sequential access and very large file sizes.
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
when the primary component becomes unavailable through either failure or
scheduled down time.
Fibre Channel (FC)
A technology for transmitting data between computer devices at data rates
of up to 1 or 2 GB/second. FC is especially suited for connecting computer
servers to shared storage devices.
file
A VLS file is a virtual cartridge.
Firesafe
The holding area for virtual media that is not assigned to a virtual library. Data
cannot be restored from virtual media located in the Firesafe until the media is
moved into a library.
hot plug
The ability to add and remove devices to an appliance while the appliance is
running and have the operating system automatically recognize the change.
infrastructure
The physical hardware used to interconnect computers. Infrastructure also
includes the software used to send, receive, and manage the signals that are
transmitted.
initiator
Media (host) server that runs the backup/restore application that passes
commands and data between the network and the VLS.
inputs/outputs per
A measure of performance for a host-attached storage device or RAID controller.
second
library
A storage device that handles multiple units of media and provides one or
more drives for reading and writing them, such as a physical tape library and
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Glossary
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