Saturday, 14 April 2018

Creating SVM-DR Relationship post 7 to C Cutover of DR and Prod

Back in September 2016, I wrote this post "Pre-StageSVM-DR Relation pre 7 to C Cutover", that was for ONTAP 8.3.2 and it was fiddly to say the least. Ever since ONTAP 9.0 you needn’t go to all that trouble.

Since ONTAP 9.0 the recommendation has been:
“Recommend migrating 7-Mode source and destination volumes to non-SVM-DR SVM’s and then creating the SVM-DR relationship post cutover. The idea being that we avoid a re-baseline and can maintain continuity of DR throughout the migration.”

The steps used to transition existing DR relationships to an SVM-DR relationship are as follows:

(1) We start with volumes being asynchronously snapmirrored from source to destination.
Note: If you have a vFiler DR configuration, this must be deleted since 7MTT does not support this (you will need to re-create the volume snapmirrors but no re-baseline is involved).

(2) Create a 7MTT secondary transition project that will coordinate snapmirror of volumes from DR 7-Mode to DR ONTAP.

(3) Create a 7MTT primary transition project that will coordinate snapmirror of volumes from Production 7-Mode to Production ONTAP

(4)  Cutover DR and then production with 7MTT, 7MTT will re-establish snapmirrors from Production ONTAP to DR ONTAP.

(5) Once cutover, you can create an SVM-DR relationship.
Note: If you want to avoid re-copies over the network, you need to cut over all the required volumes in one go, since once the you have an SVM-DR relationship you cannot 7 to C snapmirror to the disaster recovery SVM.

The simple diagram below illustrates steps 1 to 4.

Image: Transition 7-Mode DR relationships to ONTAP DR relationships

Image: Legend

How to Convert to SVM-DR

3 points to mention prior to doing the convert to SVM-DR:

- All volumes (except svm root) must be replicated
- All volumes must have same name in the source SVM and DR SVM (including svm_root)
- There will be one schedule for the SVM-DR relationship

Before creating the SVM-DR, need to decide on using ‘-identity-preserve true’ or not.

Once converted to SVM-DR, you can have some unmirrored volumes using the -vserver-dr-protection unprotected flag.

Some reading:

Converting volume replication relationships to an SVM replication relationship

Replicating SVM configurations

KB article to be aware of:

Converting volume-based SnapMirror to SVM-DR relationship fails with error: Could not determine whether msid needs to be preserved or not. Reason: Root volumes do not match


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