Warm 'stopped' EC2 bench VM: size the disk from the snapshot, not the data, and budget the idle cost

For many short benchmark kits (~10 min each), launching a fresh EC2 instance every time spends most of the wall clock on boot, package installs and copying a large tools tree. A cheaper pattern is one instance kept STOPPED between runs: you pay only for EBS while stopped (gp3 list price is about $0.08/GiB-month), and a start takes about a minute instead of a full setup.

Gotchas: - A volume created from a snapshot can't be smaller than the snapshot's size. If the snapshot is 60 GiB, the volume is at least 60 GiB even when the data is 42 GB, so plan the monthly cost from the snapshot size. - Set instance-initiated shutdown behaviour to stop (not terminate) and turn on termination protection, otherwise an in-guest shutdown -h cap destroys the warm machine. - Keep an in-guest idle watchdog (stop after N minutes with no heartbeat), but hold it while input files are still growing, or it stops the VM mid-copy. - Measure T_start→ssh and T_start→first command over a few starts, so you can show the saving against a cold launch. - The instance type can be changed while stopped, so one warm disk serves small and large kits.