Svol-Ssus Takeover In Case Of Escon/Fibre/Host Failure - Hitachi TAGMASTORE MK-90RD011-25 User Manual

4.7.4

SVOL-SSUS Takeover in Case of ESCON/Fibre/Host Failure

The SVOL-Takeover executes SVOL-SSUS-takeover to enable writing without changing the
SVOL to SMPL. SVOL-SSUS-takeover changes the SVOL to the suspend state (PAIR, PSUE
SSUS) which permits write and maintains delta data (bitmap) for all SVOLs of the group.
Host C
®
ESCON /Fibre/Host
Failure
PAIR* = PAIR for CA Sync., PAIR PSUE for Hitachi TrueCopy Async/UR.
SSUS = SVOL_PSUS
Group status of SVOL-SSUS-takeover: After SVOL-SSUS-takeover completes, the SVOL status
is displayed as SSUS by pairdisplay command, and pairvolchk command will return SVOL
status as SVOL_PSUS. Also this special state is displayed as SSWS using the -fc option of the
pairdisplay command. This special state (PVOL_PSUE and SVOL_PSUS) between PVOL and
SVOL may be needed that is handled by HA Control Script.
Hitachi TrueCopy Async/UR: Before the SVOL is changed to SSUS, the SVOL-takeover will try
to copy non-transmitted data (which remains in the FIFO queue (sidefile) of the PVOL) to the
SVOL. In case of an ESCON/FC failure, this data synchronize operation may fail. Even so, the
SVOL-takeover function will execute the force split to SSUS, enabling the SVOL to be used.
Note: Non-transmitted data (which remains in the FIFO queue (sidefile) of the PVOL) will be
reflected to the bitmap to empty the FIFO queue, and the pair state will be set to PSUE.
This non-transmitted data which is reflected to the bitmap will be lost (resynchronized as
NEW_SVOL) by issuing of the pairresync-swaps command for recovery from SVOL-SSUS-
takeover on takeover site (Host B) (see next section).
Host A
Host B
PAIR *
PAIR
PAIR *
PSUE
PAIR *
PAIR
PAIR *
PAIR
PAIR *
PAIR
P-VOL S-VOL
Hitachi Command Control Interface (CCI) User and Reference Guide
Host A
Host C
PAIR
PSUE
horctakeover
PAIR
PAIR
PAIR
P-VOL
Host B
SSUS
SSUS
SSUS
SSUS
SSUS
S-VOL
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