Hitachi MK-90RD011-25 Manual

A SERVICE OF

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110 Chapter 2 Overview of CCI Operations

Disconnected

Continue (regression)

Host A

Host B

P

Vol

S

Vol

Host A

Host B

P

Vol

S

Vol

Host A

Host B

P

Vol

S

Vol

Continue (regression)

Pairsplit -S

Paircreate

c

d

e

Entire copy

Svol goes down.

Svol recovers.

Host A

Host B

P

Vol

S

Vol

Host A

Host B

P

Vol

S

Vol

Host A

Host B

P

Vol

S

Vol

Pairresync

c

d

e

Difference

Recovery

Mirroring state

Regression state

Recovery state

c The PVOL detects a failure in the SVOL and causes suspension of the duplicated writing. (The fence level determines

whether host A continues processing or host B takes over the processing from host A.)

d The PVOL changes the paired volume status to PSUE and keeps track of the difference data. The HORCM detects the

status change and outputs a message to syslog. If the client of host A has initiated the monitoring command, the message

concerned is displayed on the screen of the client.

e The SVOL recovers from the failure. The host A issues the pairsplit -S, paircreate -vl, or pairresync command to update the

PVOL data by copying entire data or copying differential data only. The updated data is fed back to the SVOL.

Figure 2.59 Degeneracy and Recovery in Case of System Error