I know, this one caught me totally by surprise as well, but it’s true. We don’t actually use this switch when creating vmdk’s, but after seeing some _shocking_ statistics from our environment, whereby most VM’s with additional vmdk’s were using under 10% of their provisioned space, I decided to look into it.
Now I certainly don’t claim to know everything, so for non-obvious stuff like this I usually look into is as much as I can, then fire off a query to my VMware account team (well… just to the 2 engineers on our account) to see if there’s anything I have missed that would stop me from giving the OK to use it in our environment. Boy, good job I do this (and good job I have some very good SE’s)- the answer I got back isn’t covered in _any_ of the existing documentation.
The official word from VMware is that thin vmdk’s (ie those created with vmkfstools -d thin) are currently not supported for production use on FC datastores. Again, since it’s not possible to create these through the UI I imagine that there aren’t too many people out there affected by this. Even though we aren’t affected, and I can understand why VMware would take such a stance, I’m a bit miffed that there is no mention of this in any documentation I can find. I’m sure that will be changing shortly!