However, the Volume Shadow Copy Service places no restrictions on what technique the software-based providers use to create and maintain shadow copies. A software provider is applicable to a wider range of storage platforms than a hardware-based provider, and it should work with basic disks or logical volumes equally well.
A logical volume is a volume that is created by combining free space from two or more disks. In contrast to hardware shadow copies, software providers consume operating system resources to maintain the shadow copy. One shadow copy provider, the system provider, is supplied in the Windows operating system. Although a default provider is supplied in Windows, other vendors are free to supply implementations that are optimized for their storage hardware and software applications.
To maintain the "point-in-time" view of a volume that is contained in a shadow copy, the system provider uses a copy-on-write technique. Copies of the blocks on volume that have been modified since the beginning of the shadow copy creation are stored in a shadow copy storage area.
The system provider can expose the production volume, which can be written to and read from normally. When the shadow copy is needed, it logically applies the differences to data on the production volume to expose the complete shadow copy.
For the system provider, the shadow copy storage area must be on an NTFS volume. The Windows operating system includes a set of VSS writers that are responsible for enumerating the data that is required by various Windows features. In addition to backing up application data and system state information, shadow copies can be used for a number of purposes, including the following:. This is a fast-recovery scheme that allows an application administrator to restore data from a shadow copy to the original LUN or to a new LUN.
The shadow copy can be a full clone or a differential shadow copy. In either case, at the end of the resync operation, the destination LUN will have the same contents as the shadow copy LUN. During the resync operation, the array performs a block-level copy from the shadow copy to the destination LUN.
While the resync operation is in progress, read requests are redirected to the shadow copy LUN, and write requests to the destination LUN. This allows arrays to recover very large data sets and resume normal operations in several seconds. In a LUN swap, the shadow copy is imported and then converted into a read-write volume. In LUN resynchronization, the shadow copy is not altered, so it can be used several times. In LUN swapping, the shadow copy can be used only once for a recovery.
For the most safety-conscious administrators, this is important. When LUN resynchronization is used, the requester can retry the entire restore operation if something goes wrong the first time. For this reason, the shadow copy LUN must use the same quality of storage as the original production LUN to ensure that performance is not impacted after the recovery operation. If LUN resynchronization is used instead, the hardware provider can maintain the shadow copy on storage that is less expensive than production-quality storage.
All of the operations listed are LUN-level operations. If you attempt to recover a specific volume by using LUN resynchronization, you are unwittingly going to revert all the other volumes that are sharing the LUN. Shadow Copies for Shared Folders uses the Volume Shadow Copy Service to provide point-in-time copies of files that are located on a shared network resource, such as a file server.
With Shadow Copies for Shared Folders, users can quickly recover deleted or changed files that are stored on the network. Because they can do so without administrator assistance, Shadow Copies for Shared Folders can increase productivity and reduce administrative costs.
With a hardware provider that is designed for use with the Volume Shadow Copy Service, you can create transportable shadow copies that can be imported onto servers within the same subsystem for example, a SAN. These shadow copies can be used to seed a production or test installation with read-only data for data mining. With the Volume Shadow Copy Service and a storage array with a hardware provider that is designed for use with the Volume Shadow Copy Service, it is possible to create a shadow copy of the source data volume on one server, and then import the shadow copy onto another server or back to the same server.
This process is accomplished in a few minutes, regardless of the size of the data. The transport process is accomplished through a series of steps that use a shadow copy requester a storage-management application that supports transportable shadow copies.
Import the shadow copy to a server that is connected to the SAN you can import to a different server or the same server. A transportable shadow copy that is created on Windows Server cannot be imported onto a server that is running Windows Server or Windows Server R2. A transportable shadow copy that was created on Windows Server or Windows Server R2 cannot be imported onto a server that is running Windows Server However, a shadow copy that is created on Windows Server can be imported onto a server that is running Windows Server R2 and vice versa.
Shadow copies are read-only. It works only if there is a hardware provider on the storage array. Shadow copy transport can be used for a number of purposes, including tape backups, data mining, and testing.
In the case of a hard disk drive backup, the shadow copy created is also the backup. Data can be copied off the shadow copy for a restore or the shadow copy can be used for a fast recovery scenario—for example, LUN resynchronization or LUN swapping. When data is copied from the shadow copy to tape or other removable media, the content that is stored on the media constitutes the backup. The shadow copy itself can be deleted after the data is copied from it.
It depends on the backup software that you used. Most backup programs support this scenario for data but not for system state backups. It depends on the backup software you used. If you create a shadow copy on Windows Server , you cannot use it on Windows Server Also, if you create a shadow copy on Windows Server , you cannot restore it on Windows Server However, you should not do this.
VSS is designed to create shadow copies of entire volumes. Temporary files, such as paging files, are automatically omitted from shadow copies to save space. To exclude specific files from shadow copies, use the following registry key: FilesNotToSnapshot. The FilesNotToSnapshot registry key is intended to be used only by applications. Based on our experience, some third party can cause the conflict which resulting this VSS issue. In order to narrow down the cause of the issue more efficiently, let us refer the following steps to perform a Clean Boot to see if the issue still continues.
Step 1: Perform a Clean Boot. Click "Start", go to "Run", and type "msconfig" in the open box to start the System Configuration Utility. Restart your computer. Meanwhile, I would like suggest that you apply the VSS rollup update onto that problematic server. Please apply the hotfix mentioned in the following KB article. The backup application stops responding when you perform a backup that uses a volume snapshot in Windows Server with SP1.
Best Regards,. David Shen. Office Office Exchange Server. Not an IT pro? System Requirements Supported Operating System.
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