VSS data backups

You can store VSS backups on local VSS shadow volumes, or, when integrated with IBM Spectrum Protect™, in IBM Spectrum Protect server storage.

VSS backups eliminate the need for the server or file system to be in backup mode for an extended time. The length of time to complete the snapshot is measured in seconds, not hours. In addition, a VSS backup allows a snapshot of large amounts of data at one time because the snapshot works at the volume level.

You must ensure that sufficient space is available for the snapshot at the storage destination. Both storage destinations require space to store the snapshot until the data transfer to the IBM Spectrum Protect server is complete. After the data transfer to the server is complete, VSS backups that are stored locally on VSS shadow volumes are directly accessible by the system. The snapshot volume is released and the space can be reused.

  • For data that is backed up to local VSS shadow volumes, the snapshot backup is on the shadow copy volume.
  • For data that is backed up only to IBM Spectrum Protect server storage, a local snapshot backup is run and the data on the local snapshot volume is sent to the IBM Spectrum Protect server.
  • For data that is backed up to VSS shadow volumes and IBM Spectrum Protect server, the local snapshot volume is retained as a local backup after the transfer to the IBM Spectrum Protect server is complete.

If you store VSS backups both locally and to IBM Spectrum Protect server, and the maximum number of local backup versions to be maintained is reached, the oldest local backup version expires to create the new snapshot for the backup to IBM Spectrum Protect server storage. The maximum number of local backup versions that are maintained is set in the IBM Spectrum Protect policy.

Volume Shadow Copy Service framework

Volume Shadow Copy Service (VSS) provides a common interface model to generate and manage online snapshots of SQL Server data.

The Microsoft VSS service manages and directs three VSS software components that are used during VSS operations:
  • VSS writer

    The VSS writer is the application that stores data on the source volumes.

  • VSS Requestor

    The VSS Requestor is the backup software.

  • VSS provider

    The VSS provider is the combined hardware and software that generates the snapshot volume.

The VSS system provider creates and maintains snapshots on local shadow volumes and refers to the default VSS provider that is available with Windows Server. If you use the Windows VSS system provider, no configuration is required. However, you can make changes by using the VSSADMIN commands.

With a VSS hardware and software copy provider, you can create shadow copies of running volumes on demand. A hardware provider uses a hardware storage adapter or controller to manage shadow copies at the hardware level. Data Protection for SQL Server software does not control the VSS hardware provider. The VSS hardware provider is controlled by the hardware vendor. Install and configure the VSS hardware and software provider as required.