Sometimes you have a multi-disk VM where for one reason or another one of the VMDKs doesn't need to be replicated to another site for recovery. Maybe the data is meaningless like a pagefile or for whatever reason you don't want to use the bandwidth to replicate it. Perhaps it is being replicated through some other means and you just don't need it to be replicated by VR.
This is quite easy to do when using vSphere Replication. When configuring the VM for replication you simply choose to "Disable replication for this disk".
But here comes the catch. If you don't have a copy of the disk at the remote site not only will the VM expect it to be there when it recovers, but SRM will now be concerned on your behalf that the VM is not protected and it will make your protection group unhappy.
So there are a few ways around this. The first is a long and complicated process to take a clone of the non-replicated disk, zero it out but retain the UUID, copy that to the appropriate directory on the recovery site and leave it sitting there untouched so that the VM has a reference point for the 'missing' disk.
The second way is to go through the SRM interface, Configure Protection for the VM and edit the protection properties for the relevant VM. Simply click the "Detach" button associated with the appropriate VMDK.
The status of the "Recovery Site Location" will switch from "Non-replicated" to "Detached". Your protection group will go through a quick configuration step and everything will be as it should.
Keep in mind however – this means you genuinely do not have a copy of that VMDK at the recovery site! If things fail over the VM will now boot with a missing disk and this may of course cause some problems depending on what it contained, so as always: Use caution.