SRDF SRA 6.2 – Metro, Witness, and DR

Dell EMC SRDF SRA 6.2 is now available for download and use with the latest HYPERMAX OS Q3 SR. This SRA brings support for a couple features which greatly enhance SRDF/Metro capabilities in SRM. The first is the ability to use the SRA with a Metro pair that is protected by a Witness (physical or virtual) rather than Bias. This means that if there is a failure in the environment, either the R1 or the R2 will survive, rather than only the Bias site winning (if the Bias side fails, the R2 is not readily available). This is the benefit of having the Witness as arbiter. When the Witness is in use, within SRM the pair will show no site preference as below.

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The second, and arguably more significant feature with the SRA 6.2 is support for 3-site replication with SRDF/Metro. Three-site replication (non-Star) was introduced in the Q3 SR. This now provides a DR component along with the HA that SRDF/Metro brings. The SRA supports both concurrent and cascaded configurations, running in asynchronous mode. Here is an example of a concurrent configuration. Pair 3C and 4A have an ActiveActive relationship and 3C also has a cascaded, asynchronous relationship with device 39.


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In the consolidated view we can also see that Witness is being used.


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In 3-site configurations in SRM remember that you can only configure either the R2 of the SRDF/Metro pair, or the asynchronous (cascaded or concurrent) pair for failover. If you want to use the asynchronous site be sure to modify the global options file on each site to permit the use of the async leg:


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If you don’t plan on using the asynchronous site there is no requirement to have compute resources there. In my environment below you can see the RDF device pair of 3C and 39:


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An important caveat to using a 3-site setup with SRDF/Metro, is that if you plan to use the asynchronous leg in SRM, you cannot have both a concurrent and a cascaded leg. If you will use the Active pair and are only using the asynchronous leg as manual recovery, then it is conceivable to have a relationship off the R1 and R2.

In addition to the engineering release of SRDF SRA 6.2, the solutions organization is releasing the SRDF Adapter Utilities (SRDF-AU) 6.2 which will support the SRA. The SRDF-AU is an optional plug-in which provides a GUI interface to modify the XML files of the SRA. The SRDF-AU is only supported in SRM environments that have either the protected or recovery site running on a Windows vCenter.  There is no support for the vCenter Appliance (VCSA), nor is there currently a roadmap for that support. Be sure to read the SRDF-AU Release Notes thoroughly as there is a bug that will impact SMI-S connectivity. It will require changing a security file or setting up a non-SSL port.

I have published an update to my SRDF SRA TechBook which contains all the new information and additional considerations around using SRDF/Metro. In addition, I created an Appendix that contains technical information which mirrors that found in the SRA Release Notes. The date on the front should say October 2016. The link is for which requires a login, but the one should be available soon and you can find the link in the Important Docs page above.



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