I have two Netapp filers running ONTAP 7-mode with some volumes on the main one replicated to the secondary one on another site. I need to regularly test my DR, but I can't break the replication during the test. Sometimes they're quite long, and a lot of changes happen to the main system's replicated volumes that would be lost, if we had a real DR during a DR test. Also, I'd risk falling behind by a couple of days of replication, which could take a lot longer to catch up on.
I want to clone the replicated volumes to test them, however the snapmirror targets are read-only, so I can't take a snapshot for the clone.
The only way to do a DR test with this type of environment is to take snapshots on the main site, wait for them to replicate, and then use the replicated snapshot as a base for the clone on the secondary site.
Basically, when you have an active snapmirror, the snapshots on the target volume are kept up to date with the source volume. You can't have a snapshot on the secondary site without creating it on the primary site and then waiting for an update.
Be very careful about deletion of snapshots from your main site- if you delete a snapshot on a snapmirror source but there's an active clone on the remote site, that clone will lock the snapshot on the remote site, and your replication will halt until you delete the clone. The default setting for snapshot autodelete is to delete manual snapshots last, but be aware that if your autodelete setting end up clobbering the snapshot that's in use on the other side, your replication will stop.