IBM System storage DS6000 Series, Redbook

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IBM System Storage DS6000 Series: Copy Services with IBM System z
Figure 23-8 shows more than a single FICON/FCP director at both sites, for availability
reasons. Note that the Master and Subordinate paths are defined over a local SAN fabric,
represented by the FICON/FCP directors.
23.7 Recovery scenario after primary site failure
This section covers the steps that you need to follow in a Global Mirror environment, when a
primary site failure requires you to recover at the secondary site. This discussion does not
cover the specifics concerning whether it is a single site host connectivity scenario or
multi-site host connectivity scenario, as discussed in 23.6, “Connectivity between local and
remote site” on page 279.
23.7.1 Normal Global Mirror operation
Figure 23-9 shows a simple configuration with Global Mirror active and running.
Figure 23-9 Normal Global Mirror operation
Host writes are replicated through Global Copy. Consistency Groups are created as tertiary
copies. The B volumes are Global Copy secondary volumes, and they are also FlashCopy
source volumes. The C volumes are the FlashCopy target volumes.
23.7.2 Primary site failure
A failure at the local site prevents all I/O to the local storage disk subsystems; see
Figure 23-10. This may have some impact on the formation of Consistency Groups because
the entire process is managed and controlled by the Master storage disk subsystem that is
also the primary disk subsystem—and it just failed, and cannot communicate any longer with
its partners at the remote site.
FlashCopy
Global Copy
Primary
Primary
A
Primary
Primary
A
Primary
A
Primary
Primary
A
Primary
Primary
A
Tertiary
C
Primary
Primary
A
Primary
Primary
A
Secondary
B
3E00
3F00
Host
Remote site Local site
PENDING
PENDING