6 svol-takeover in case of host failure – Hitachi TAGMASTORE MK-90RD011-25 User Manual

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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 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

S-VOL

Host C

Host A

Host B

PSUS

SSUS

P-VOL

S-VOL

Host C

Host A

Host B

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

horctakeover

P-VOL

S-VOL

P-VOL

Host C

Host A

Host B

PAIR

PSUE

PAIR

SSUS

S-VOL

horctakeover

Host D