When creating EBS snapshots, it’s important that the snapshots be “consistent”. This means that the data on the snapshot is whole and complete. An EBS snapshot can be considered “inconsistent” if not all data was flushed to the filesystem, and/or if an application running on the EC2 instance was mid-write when the EBS snapshot was initiated.
AWS recommends pausing all writes to the filesystem, and if that’s not possible, unmounting the volume from your EC2 instance when creating the EBS snapshot. However, that’s not possible for root EBS volumes.
For many years, Skeddly has included a “Stop Instance” consistency method when creating EBS snapshots. Stopping the EC2 instance is another way to ensure all data written to the EBS volume is flushed to the hardware. With this option enabled, Skeddly briefly shuts down the EC2 instance, initiates the EBS snapshot, then restarts the EC2 instance. Usually, the EC2 instance is stopped for only a minute or so. But, in some cases, even this brief moment of unavailability is not allowed.
If you are using Windows, you can use a feature called Volume Shadow Copy, or VSS for short, to help create consistent snapshots. AWS has an SSM document in AWS Systems Manager that you can use to create VSS-Enabled EBS snaphots.
Today, we’re making available a VSS option to our EBS snapshot actions that you can use to automate the creation of VSS-enabled EBS snapshots.
VSS-enabled EBS snapshots can be created with any of these Skeddly action types:
as well as when creating EBS snapshots using Skeddy’s Managed Instances.
To enable VSS snapshots, choose one of these options as a “Consistency Method”:
You’ll notice a fallback method in each option. This fallback is used if you’re using Linux or if your Windows instance does not meet the SSM requirements. So you can use VSS where VSS is supported, and “Stop Instance” for all others.
Our implementation utilizes AWS’s support for VSS-enabled EBS snapshots. But we’ve improved upon it, allowing you to take advantage of many EBS snapshot features in Skeddly.
Skeddly’s IAM Policy Generator will include all necessary commands needed to:
For more information about this feature, along with setting it up, please read A Guide to Creating VSS-Enabled EBS Snapshots.
There is no extra cost for this feature above the normal EBS snapshot costs.