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210 Chapter 4 Performing CCI Operations
4.7.6 SVOL-Takeover in Case of Host Failure
After SVOL-takeover changed to the suspend (PAIR, PSUE Æ SSUS) state with the SVOL only,
internal operation of SVOL-takeover will be executed pairresync -swaps command for
maintaining mirror consistency between NEW_PVOL and NEW_SVOL, and then will be
returned with Swap-takeover as the return value of horctakeover command.
Hitachi TrueCopy Async/UR. Before the SVOL is changed to SSUS, the SVOL-takeover will
copy non-transmitted data (which remains in the FIFO queue (sidefile) of the PVOL) to the
SVOL side. The SVOL-takeover operation is waited to copy non-transmitted data of the PVOL
before a timeout value (that is specified by -t <timeout> option). After the completion of a
synchronous state between the PVOL and SVOL, the SVOL-takeover will be split and the state
will be changed to SSUS, and the operation of after that is same.
horctakeover
P-VOL
Host C
Host A
Host B
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
S-VOL
Host C
Host A
Host B
PSUS
PSUS
PSUS
PSUS
PSUS
SSUS
SSUS
SSUS
SSUS
SSUS
P-VOL S-VOL
Host C
Host A
Host B
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
PAIR
S-VOL P-VOL
Before running APP
internally execute
pairresync -swaps
Since the SVOL has been the SSWS already as state of the SVOL_SSUS takeover after, the
horctakeover command will do nothing in this nested failure case.
Host C
Host A
Host B
PAIR
PSUE
PAIR
PAIR
PAIR
SSUS
SSUS
SSUS
SSUS
SSUS
horctakeover
P-VOL S-VOL
P-VOL
Host C
Host A
Host B
PAIR
PSUE
PAIR
PAIR
PAIR
SSUS
SSUS
SSUS
SSUS
SSUS
S-VOL
horctakeover
Host D
Host D