It also takes a few seconds on AWS. The guy is comparing setting up a whole new machine from an image, with network and all, to turning on a stopped EC2 instance.
The latter takes a few seconds, the former is presumably longer. This is the great relevation of this blog post.
I think this is unexpected. I expected that once created, my boot volume would have the same performance on the first boot than on the second. It's really not obvious that the volume is really empty and lazily loaded from S3. The proposed work around is also a bit silly: read all blocks one by one even tho maybe 1% of the block have something in them on a new VM. This is actually a revelation.
If you aren't familiar with how EBS works and how volumes are warmed, then yes, this is an interesting blog post. Not everyone is an expert. They become experts by reading things like this and learning.
If you didn't know about this EBS behavior it would be logical to assume that booting from scratch is roughly equivalent to starting/stopping/starting again.
Intuitively, I would have expected AWS to send back the EBS volume backing a powered-off machine into the Whatever Long-Term Storage Is Behind EBS, and therefore start-up time to be ~identical to a fresh start as the steps would be the same: retrieve data from long-term storage into a readable EBS volume, start VM etc.
It's very interesting that it is not the case, and that keeping the EBS volume around after a first boot makes a second boot so much faster.
If that were the case, then there would be absolutely no benefit from having a stop vs terminate. Unless you've written data to the EBS volume, but in these cases where the boot time is critical most of them are some sort of read-only volume anyways. The fact that an EC2 can be stopped or terminated should immediately suggest speed might be a difference in reaching the running state. In the EBS docs, it clearly states that if you keep an EBS volume around either attached to a stopped EC2 or detached and left in your pool of volumes, you will be charged for that volume.
The latter takes a few seconds, the former is presumably longer. This is the great relevation of this blog post.