Re: Roll your own
"Made our own Nutanix style offering for our clients which scales well and is about 1/3 the cost of traditional HCI boxes from the big vendors.
I'm sure Linux has an equally good offering too."
Totally agree that there's many ways of skinning the HCI cat. We've found very similar savings running our own using OpenStack + Ceph on SuperMicro kit and it takes a lot less work to deploy and maintain than the HCI vendors would have you believe.
Storage Spaces Direct looks pretty compelling these days too.