Hello Kevin,   You are correct, setting the snapshot reserve to 0% does not have any impact on volume performance. It just returns that space to the free space and prevents snapshots from being created.   I suspect he was thinking about what happens when you run a member totally out of free space when using thin provisioned volumes and you've over provisioned it.   As the end of free space approaches writes will be slowed down.  Once there is no more free space, thin provisioned volumes needing more space will go offline until the problem is corrected.   Regards,   Don 
I have a Dell PS6100 that we use for our VM storage. I had one of our contracted techs tell me today that by setting Snapshot reserve to 0% (we don't use them), that he learned in his Dell class years ago that this would cause "a drop in IOP performance". This sounds like gabarge to me. I've disabled snapshots on SANs before in the past and never seen a performance hit or ever heard of that being the case. Technically it doesn't make sense to me. Thought I would double check though as I've been wrong before. Thoughts?
Snapshots Reserve