Estimating AWS EC2 EBS Snapshots

Estimating and understanding what AWS EC2 EBS Snapshots will cost you can be more difficult than you may think.

Here are some key points to keep in mind:

  • Snapshots are not compressed. Therefore your first snapshot will be equal to the GiB used in the source EBS volume.
  • Additional snapshots are incremental. Each incremental snapshot uses pointers, pointing to the prior snapshot’s blocks that have not changed. New blocks are recorded.
  • You can use the AWS Cost Explorer to view past usage. Today is not available. Filter down by “Usage Type Group” and set the value to “EC2: EBS – Snapshots”. Narrow down further by region and/or tag.
    • Usage (GB) are measured by “GB-Month”. So if there are 30 days in that month, multiple the metric by 30 to get that day’s actual usage.
  • As of 12/10/2018, the cost of a snapshot is $0.05/GB/mo

The hard part is estimating the amount of change per snapshot. The most lenient method would be to use a 100% change value. But that’s not practical.

Let’s say you estimate that 3% of your total volume size will be modified per snapshot. Therefore plan on an additional cost of $.15/mo for every 100 GiB of used volume space on every snapshot produced..