What is VSS? - Amazon Elastic Compute Cloud

What is VSS?

Volume Snapshot Copy Service (VSS) is a backup and recovery technology included in Microsoft Windows. It can create backup copies, or snapshots, of computer files or volumes while they are in use. For more information, see Volume Shadow Copy Service.

To create an application-consistent snapshot, the following software components are involved.

  • VSS service — Part of the Windows operating system

  • VSS requester — The software that requests the creation of shadow copies

  • VSS writer — Typically provided as part of an application, such as SQL Server, to ensure a consistent data set to back up

  • VSS provider — The component that creates the shadow copies of the underlying volumes

The Windows VSS based Amazon EBS snapshot solution consists of multiple Systems Manager (SSM) Run Command documents that facilitate backup creation, and a Systems Manager Distributor package, called AwsVssComponents, that includes an EC2 VSS requester and an EC2 VSS provider. The AwsVssComponents package must be installed on EC2 Windows instances to take application-consistent snapshots of EBS volumes. The following diagram illustrates the relationship between these software components.

VSS software components

How the VSS based Amazon EBS snapshot solution works

The process for taking application-consistent, VSS based EBS snapshot scripts consists of the following steps.

  1. Complete the Prerequisites.

  2. Enter parameters for the AWSEC2-VssInstallAndSnapshot SSM document and run this document by using Run Command. For more information, see Run the AWSEC2-VssInstallAndSnapshot command document (recommended).

  3. The Windows VSS service on your instance coordinates all ongoing I/O operations for running applications.

  4. The system flushes all I/O buffers and temporarily pauses all I/O operations. The pause lasts, at most, ten seconds.

  5. During the pause, the system creates snapshots of all volumes attached to the instance.

  6. The pause is lifted and I/O resumes operation.

  7. The system adds all newly-created snapshots to the list of EBS snapshots. The system tags all VSS-enabled EBS snapshots successfully created by this process with AppConsistent:true.

  8. If you need to restore from a snapshot, you can use the standard EBS process of creating a volume from a snapshot, or you can restore all volumes to an instance by using a sample script, as described in Restore EBS volumes from VSS-enabled EBS snapshots.