Figure 43 SRDF/Metro Array Witness and groups
SRDF links
R1 array
R2 array
R1
R2
SRDF/Metro Witness array:
S
RDF Witnes
s group
S
R
DF Witness gro
up
Solutions Enabler checks that the Witness groups exist and are online when carrying
out establish or restore operations. SRDF/Metro determines which witness array an
SRDF/Metro group is using, so there is no need to specify the Witness. Indeed, there
is no ability to specify the Witness.
When the witness array is connected to both the SRDF/Metro paired arrays, the
configuration enters Witness Protected state.
When the Array Witness method is in operation, the state of the device pairs is
ActiveActive.
If the witness array becomes inaccessible from both the R1 and R2 arrays,
HYPERMAX OS sets the R1 side as the bias side, the R2 side as the non-bias side, and
the state of the device pairs becomes ActiveBias.
Virtual Witness (vWitness)
Virtual Witness (vWitness) is an additional resiliency option introduced in HYPERMAX
OS 5977.945.890 and Solutions Enabler or Unisphere for VMAX V8.3. vWitness has
similar capabilities to the Array Witness method, except that it is packaged to run in a
virtual appliance (vApp) on a VMware ESX server, not on an array.
The vWitness and Array Witness options are treated the same in the operating
environment, and can be deployed independently or simultaneously. When deployed
simultaneously, SRDF/Metro favors the Array Witness option over the vWitness
option, as the Array Witness option has better availability. For redundancy, you can
configure up to 32 vWitnesses.
Remote replication solutions
SRDF/Metro resiliency 151
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