controller
The component in a storage system that manages all storage functions. It is analogous
to a computer and contains a processors, I/O devices, RAM, power supplies, cooling
fans, and other sub-components as needed to support the operation of the storage
system.
copy-after-write
Point-in-time snapshot copy of a data volume within a storage system. Copy-after-write
snapshots only store changed data blocks, therefore the amount of storage capacity
required for each copy is substantially smaller than the source volume.
copy pair
A pair of volumes in which one volume contains original data and the other volume
contains the copy of the original. Copy operations can be synchronous or asynchronous,
and the volumes of the copy pair can be located in the same storage system (local
copy) or in different storage systems (remote copy).
A copy pair can also be called a volume pair, or just pair.
CTG
See consistency group (CTG).
CTL
controller
CU
control unit
currency of data
The synchronization of the volumes in a copy pair. When the data on the secondary
volume (S-VOL) is identical to the data on the primary volume (P-VOL), the data on the
S-VOL is current. When the data on the S-VOL is not identical to the data on the P-VOL,
the data on the S-VOL is not current.
CYL, cyl
cylinder
cylinder bitmap
Indicates the differential data (updated by write I/Os) in a volume of a split or
suspended copy pair. The primary and secondary volumes each have their own cylinder
bitmap. When the pair is resynchronized, the cylinder bitmaps are merged, and the
differential data is copied to the secondary volume.
D
DASD
direct-access storage device
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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
Glossary-5
Hitachi TrueCopy® User Guide for Hitachi Virtual Storage Platform Gx00 and Fx00 Models
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