My understanding is that EBS has some heuristics for deciding whether to keep data cached; an AMI which has a cached snapshot as its root disk will boot much faster than an AMI where all the data needs to be pulled from S3.
What's the smallest size for which those heuristics keep the snapshot cached?
(I'm currently using 1GB snapshots, because my actual disk image is a tiny fraction of that size. But if bumping that to 2GB or 4GB would make it faster, that's a small price to pay.)
Do you have any other wisdom regarding mysterious reasons for fast or slow booting? EC2's boot process is deeply opaque, and any insight at all is better than nothing.
