Shadow Copies 101: What Are They & How Do They Work?

July 27th, 2017
Vadim VladimirskiyFounder & CEO, Nerdio

Shadow Copy (Volume Shadow Copy Service, Volume Snapshot Service, or VSS) takes both automatic and manual backup duplicates of volumes or files within a computer. This technology can take snapshots or identical versions of the volumes even when they are in use. This technology is applicable for Windows 7, Windows Server 2003, 2008, 2012, and 2016, Windows Server 2008 R2, and Windows Vista.

The process of restoring and backing up sensitive business information is highly complex for two reasons. First, large data sets can be difficult to back up all at once. Second, the applications that generate the data must often continue running while the data backup is taking place, meaning that certain files may be inconsistent or in use during the backup.

VSS synchronizes the specific actions that are essential to producing an accurate backup version of data. Shadow Copies can be utilized for the following situations, or may be used on their own:

  • Data mining
  • Disk-to-disk backup
  • Data backup to removable media or a hard disk drive
  • Restoring data for quick recovery from data loss

Windows® applications that utilize VSS are System Restore, Windows Server Backup, System Center Data Protection Manager, and Shared Folders.

data mining

How Shadow Copies work

VSS technology incorporates the four segments listed below.

  • VSS Service: This service enables the components within the Windows operating system to work together and communicate properly.
  • VSS Requester: The requester is responsible for creating, importing and deleting the Shadow Copies. This is normally the backup application. Examples of VSS requesters are the System Center Data Protection Manager and the Windows Server Backup utility.
  • VSS Writer: The writer ensures that there is always a reliable data set that can be backed up. Exchange Server, SQL Server® and other applications will normally include a VSS writer within a product set. Windows operating systems include VSS writers for several components, including the registry. Many applications for Windows also include third-party VSS writers when data-backup guarantees are needed.
  • VSS Provider: The provider is responsible for creating and maintaining the Shadow Copies, and it does so within the hardware or software. The VSS provider creates and maintains the duplicate version from the host operating system.

How to enable and configure Shadow Copies for use with shared folders

Tasks are pre-scheduled; Shadow Copies are created at 7:00 a.m. and again at noon unless the user manually configures the schedule. The storage area will not exceed more than the allotted volume, and it will utilize 10 percent of the available space (but that’s just the default – more than likely whomever is configuring VSS will want to increase the available space so they can have more snapshots retained).

This technology can only be enabled as a part of the entire volume with shared folders. This means that specific shared folders or files within a volume cannot be duplicated or excluded separately. To configure and enable VSS of Shared Folders, complete the following steps.

  1. Open Computer Management.
  2. Right-click Shared Folders from within the management console tree, select All Tasks, then select Configure Shadow Copies.
  3. Select the volume where you want Shadow Copies of shared folders to be enabled, and select Enable.
  4. Select Settings to change the default storage area and schedule.

taking advantage of shadow copies

How to take advantage of Shadow Copies

The following recommendations are best practices for utilizing Shadow Copies with shared folders.

  • Utilizing a different volume on a separate disk from the storage area is ideal for better performance.
  • Determine the ways in which clients will utilize the shared resource before enabling Shadow Copies of shared folders and setting scheduling options.
  • Do not permit this feature to be enabled for volumes with mount points, as there will be no mounted drive contained within the Shadow Copy.
  • Back up your file server regularly, as this feature is not meant to replace regular data backups.
  • Do not enable Shadow Copy to be run more than once an hour.
  • Delete the task that created the Shadow Copies prior to deleting a volume that will be Shadow Copied.
  • When formatting a source volume for which Shadow Copies of shared folders will be enabled, utilize a 16-kilobyte or larger cluster allocation unit size.
  • Do not restore a volume containing previously created copies to a computer that has already been backed up.

The backing up of Shadow Copies is complex because it is vital to the proper completion of backup and restore processes. The applications that are being backed up, the backup applications themselves, and the storage management hardware and software must be carefully managed in order to properly complete the backup and restore operations. This technology makes it easier for you to ensure your data is backed up while continuing to operate at full capacity.