After my recent post on EC2 Micro instances, I received a great comment from Robert Jenkins over at CloudSigma regarding the “false construct” of fixed instance sizes. There’s no reason why an EC2-small has to have 1.7GB RAM, 1 VPU and 160GB of local storage. The underlying virtualization technology allows for fairly open configurability of instances. What if I want 2.5GB of RAM, 2 VPUs and 50GB of local storage? I can’t get that from Amazon – but the Xen hypervisor they doesn’t prohibit this. You’re never going to use exactly 160GB of storage, and Amazon is counting that most won’t use more than 50 or 60 GB – showing you how much of a deal you get for something they never have to provide.
Same is true for most cloud providers. Rackspace allows you to go down to 256mb RAM, 10GB disk and then a 10Mbps bandwidth limit. You can use more bandwidth and disk, you just pay for it.
Perhaps customers like the “value meal” approach with pre-configured instance types and they sell better. Perhaps Amazon likes being able to release a new instance type every quarter as a way to generate news and blog posts. Perhaps their ecommerce billing systems can’t handle the combinatorial complexity of variable memory, storage, bandwidth and VPUs. Whatever the reason, these fixed instance types limit user choice.
They’re dumb because they’re unnecessary.