Instead of a single allocation, EC2 announced you can run several different kinds of instances.

See the EC2 home page for details:

$0.10 – Small Instance (Default)

1.7 GB of memory, 1 EC2 Compute Unit (1 virtual core with 1 EC2 Compute Unit), 160 GB of instance storage, 32-bit platform

$0.40 – Large Instance

7.5 GB of memory, 4 EC2 Compute Units (2 virtual cores with 2 EC2 Compute Units each), 850 GB of instance storage, 64-bit platform

$0.80 – Extra Large Instance

15 GB of memory, 8 EC2 Compute Units (4 virtual cores with 2 EC2 Compute Units each), 1690 GB of instance storage, 64-bit platform

In many cases it may be more cost effective to still get the small instance but just get a lot of them, this will be interesting for our workspace EC2 adapter and contextualization users (and us!). Once we make the small alterations to accomodate requesting these types, it will be just as easy to get 100 x small instance as 25 x large instance, or whatever combination, because deployment configurations can be coordinated on the fly. What would be best for what situation would have to be examined closely. An extra large instance for the virtual cluster head node(s) or storage/transfer node(s) could be extremely useful for the typical grid-cluster bottlenecks.