EMC VMAX 200K - Page 150

symrdf -f /tmp/device_file -sid 085 -rdfg 86 establish -use_bias
If the Witness options are not used, the establish and restore commands also
require the use_bias option.
When the SRDF/Metro devices pairs are configured to use bias, their pair state is
ActiveBias.
Bias can be changed when all device pairs in the SRDF/Metro group have reached the
ActiveActive or ActiveBias pair state.
Array Witness
When using the Array Witness method, SRDF/Metro uses a third "witness" array to
determine the bias side. The witness array runs one of the following operating
environments:
l
Enginuity 5876 with ePack containing fixes to support SRDF N-x connectivity
l
HYPERMAX OS 5977.810.784 with ePack containing fixes to support SRDF N-x
connectivity
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HYPERMAX OS 5977.945.890 or later
In the event of a failure, the witness decides which side of the Metro group remains
accessible to hosts, giving preference to the bias side. The Array Witness method
allows for choosing on which side to continue operations when the Device Bias
method may not result in continued host availability to a surviving non-biased array.
The Array Witness must have SRDF connectivity to both the R1-side array and R2-
side array.
SRDF remote adapters (RA's) are required on the witness array with applicable
network connectivity to both the R1 side and R2 side arrays.
For complete redundancy, there can be multiple witness arrays. If the auto
configuration process fails and no other applicable witness arrays are available, SRDF/
Metro uses the Device Bias method.
The Array Witness method requires 2 SRDF groups; one between the R1 array and the
witness array, and a second between the R2 array and the witness array:
Note
A Witness group is not allowed to contain devices.
Remote replication solutions
150 Product Guide VMAX 100K, VMAX 200K, VMAX 400K with HYPERMAX OS