Hitachi MK-97DF8018-00 - Manual (Page 77)

Glossary–5
Hitachi Simple Modular Storage Copy-on-Write SnapShot User’s Guide
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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
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data pool
One or more disk volumes designated to temporarily store un-
transferred differential data (in the local storage system or snapshots
of backup data in the remote storage system). The saved snapshots are
useful for accurate data restoration (of the P-VOL) and faster remote
takeover processing (using the S-VOL).
data volume
A volume that stores database information. Other files, such as index
files and data dictionaries, store administrative information (metadata).
differential data control
The process of continuously monitoring the differences between the
data on two volumes and determining when to synchronize them.
differential data copy
The process of copying the updated data from the primary volume to
the secondary volume. The data is updated from the differential data
control status (the pair volume is under the suspended status) to the
primary volume.
Differential Management Logical Unit (DM-LU)
The volumes used to manage differential data in a storage system. In a
TrueCopy Extended Distance system, there may be up to two DM
logical units configured per storage system. For Copy-on-Write and
ShadowImage, the DM-LU is an exclusive volume used for storing data
when the array system is powered down.
differential-data
The original data blocks replaced by writes to the primary volume. In
Copy-on-Write, differential data is stored in the data pool to preserve
the copy made of the P-VOL to the time of the snapshot.
disaster recovery
A set of procedures to recover critical application data and processing
after a disaster or other failure. Disaster recovery processes include
failover and failback procedures.
disk array
An enterprise storage system containing multiple disk drives. Also
referred to as “disk array device” or “disk storage system.”
DM-LU
See Differential Management-Logical Unit.