EMC VMAX 200K - SRDF Device States; R21 Device in Cascaded SRDF; R22 Devices in Cascaded and Concurrent Srdf;Star

Figure 27 R21 device in cascaded SRDF
Site BSite A
SRDF Links
Production
host
Site C
R1
R21
R2
When the R1->R21->R2 SRDF relationship is established, no host has write access to
the R21 device.
Note
Diskless R21 devices are not supported on arrays running HYPERMAX OS.
R22 devices
R22 devices:
l
Have two R1 devices, only one of which is active at a time.
l
Are typically used in cascaded SRDF/Star and concurrent SRDF/Star solutions to
decrease the complexity and time required to complete failover and failback
operations.
l
Let you recover without removing old SRDF pairs and creating new ones.
Figure 28
R22 devices in cascaded and concurrent SRDF/Star
SRDF/S
Site A
SRDF/A
Site C
SRDF/S
Site B
Active
links
Host
Host
Site B
Site A
Site
C
SRDF/A SRDF/A
SRDF/A
Cascaded STAR Concurrent STAR
Inactive
links
R22
R2
R11
R21
R11
R21
SRDF device states
An SRDF device’s state is determined by a combination of two views; host interface
view and SRDF view, as shown in the following image.
Remote replication solutions
SRDF device states 119