24 Chapter 2 Overview of CCI Operations
Pair resynchronization: The pairresync command resynchronizes the secondary volume
based on the primary volume. This resynchronization does not guarantee the sequenced
data transfer.
Error suspending: Pending recordsets which have not yet been sent to the secondary
volume are marked on the bitmap of the primary volume and then deleted from the
queue, and then the pair status changes to PSUE.
Group operations: HORCM registers CTGID to the storage system automatically when
paired volumes are created by the paircreate command, and groups of configuration file
are mapped to CTGID. If more than one group defined in the configuration definition file
is assigned to the same CT group ID, then pair operations of the group specification
apply to the entire CT group.
R/W
Resynchronization
Asynchronous transfer
Process-A
write(1)
.
write(4)
write(5)
Process-B
write(2)
.
write(3)
HA Software Package
BITMAP
Primary
volume
PAIR
PSUS / PSUE
BITMAP
FIFO
Primary
volume
BITMAP Secondary
volume
BITMAP
FIFO
Secondary
volume
CT group
Hitachi RAID Storage
Hitachi RAID Storage
PSUE PSUE
PAIR
Note: Write() shows that synchronous writing or
commit() of DB is used.
5 4 3
. . . . . . . . . .
2 1
. . . . . . . .
Figure 2.9 Hitachi TrueCopy Asynchronous Consistency Groups
