I realize there's no one size fits all for datastore sizing these days, but I'd like to know on what criteria I should be basing my opinions.
I'm on ESXi 6.0, and still rocking 2 Tb datastores. For servers requiring larger disks (mostly MS SQL or Oracle db's), I use RDM's as to not bogart an entire datastore or create one bigger than my norm. I had a backup vendor challenge me as to why I was still using RDM's and smaller datastores. I suspect his comments may have partly been because most backup platforms still struggle with RDM's, but I wondered if his comments held any weight and I should be rethinking my architecture decisions.
What criteria do you include/use when choosing how big your datastores should be?