I'm working on a project that involves running a lot of spot instances over a short period of time, then terminating the spot reservation and starting the instances with a different AMI. If I reserve 500 spot EBS-backed EC2 instances for a day and they all have 8GB hard drive, am I paying for 500 EBS-days or 500 EBS-months (multiplied by 8GB)? If the latter, will terminating the instances and asking for new ones mean that I'm paying for another 500 EBS-months even if I use the machines just for one day?

1 Answer 1


Neither, really. EBS bills by hours. https://aws.amazon.com/ebs/pricing/

Volume storage for General Purpose SSD (gp2) volumes is charged by the amount you provision in GB per month, prorated to the hour, until you release the storage.

  • It sounds more like the former then - by "EBS-days" I meant "24x EBS-hours". Thanks for clarifying this, though.
    – d33tah
    Mar 13, 2017 at 18:03
  • @d33tah Yes, essentially, but if your systems kill an instance at 19:30 hours you'll only pay for the 20 you used. Enjoy!
    – ceejayoz
    Mar 13, 2017 at 18:05

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