Each writer prepares the data as appropriate, such as completing all open transactions, rolling transaction logs, and flushing caches. When the data is ready to be shadow-copied, the writer notifies the Volume Shadow Copy Service. The application freeze is not allowed to take longer than 60 seconds. The Volume Shadow Copy Service flushes the file system buffers and then freezes the file system, which ensures that the file system metadata is recorded correctly and the data to be shadow-copied is written in a consistent order.
The Volume Shadow Copy Service tells the provider to create the shadow copy. At this point applications are free to resume writing data to the disk that is being shadow-copied. The shadow copy creation can be aborted if the writers are kept in the freeze state for longer than 60 seconds or if the providers take longer than 10 seconds to commit the shadow copy.
The requester can retry the process go back to step 1 or notify the administrator to retry at a later time. If the shadow copy is successfully created, the Volume Shadow Copy Service returns the location information for the shadow copy to the requester. In some cases, the shadow copy can be temporarily made available as a read-write volume so that VSS and one or more applications can alter the contents of the shadow copy before the shadow copy is finished.
After VSS and the applications make their alterations, the shadow copy is made read-only. This phase is called Auto-recovery, and it is used to undo any file-system or application transactions on the shadow copy volume that were not completed before the shadow copy was created.
A hardware or software shadow copy provider uses one of the following methods for creating a shadow copy:. Complete copy This method makes a complete copy called a "full copy" or "clone" of the original volume at a given point in time. This copy is read-only. Copy-on-write This method does not copy the original volume. Redirect-on-write This method does not copy the original volume, and it does not make any changes to the original volume after a given point in time.
Instead, it makes a differential copy by redirecting all changes to a different volume. After the mirror connection is broken, the original volume and the shadow copy volume are independent.
The shadow copy storage area can be on the same volume or a different volume. This preserves a copy of the data block on the original volume before the change overwrites it. The copy-on-write method is a quick method for creating a shadow copy, because it copies only data that is changed. The copied blocks in the diff area can be combined with the changed data on the original volume to restore the volume to its state before any of the changes were made.
If there are many changes, the copy-on-write method can become expensive. Instead, the change is written to another volume's shadow copy storage area.
Like the copy-on-write method, the redirect-on-write method is a quick method for creating a shadow copy, because it copies only changes to the data. The copied blocks in the diff area can be combined with the unchanged data on the original volume to create a complete, up-to-date copy of the data.
There are two types of shadow copy providers: hardware-based providers and software-based providers. There is also a system provider, which is a software provider that is built in to the Windows operating system. Hardware-based shadow copy providers act as an interface between the Volume Shadow Copy Service and the hardware level by working in conjunction with a hardware storage adapter or controller. The work of creating and maintaining the shadow copy is performed by the storage array.
Hardware providers always take the shadow copy of an entire LUN, but the Volume Shadow Copy Service only exposes the shadow copy of the volume or volumes that were requested. A hardware-based shadow copy provider makes use of the Volume Shadow Copy Service functionality that defines the point in time, allows data synchronization, manages the shadow copy, and provides a common interface with backup applications.
However, the Volume Shadow Copy Service does not specify the underlying mechanism by which the hardware-based provider produces and maintains shadow copies. These providers are implemented as a user-mode DLL component and at least one kernel-mode device driver, typically a storage filter driver. Unlike hardware-based providers, software-based providers create shadow copies at the software level, not the hardware level.
A software-based shadow copy provider must maintain a "point-in-time" view of a volume by having access to a data set that can be used to re-create volume status before the shadow copy creation time. An example is the copy-on-write technique of the system provider. 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. When encountering system image restore failed volume shadow copy service issue, you can still fix it. If the 0x error is triggered when opening the System Restore utility, it can be fixed by a clean boot. Follow these steps:.
Step 2: Under the General tab, uncheck the Load startup items from the Selective startup menu. In this part, we have shown you four VSS errors which happen when you are creating a system image or performing a system restore with the Windows built-in backup and restore utility.
By following the corresponding solution, probably you can fix it. Click to tweet. But recently some of you turn to us for help, saying " is there anyone alternative to Windows Backup and Restore so as to effectively create a system image and restore the image ".
The answer is yes. Here, we will show you one free backup software from MiniTool Solution Ltd. As an excellent backup solution, this freeware lets you not only create scheduled backups by setting the specific time point but also set incremental and differential backups for the only changed or newly added data.
In the event of system accidents, the image file is available to restore the system to its previous state with simple clicks. Now, get the Trial Edition of this backup software for days free trial. Step 1: After completing the installation of this tool on your computer, open it to the main interface.
Step 2: It's the time to choose the partitions you want to backup and decide the location you want to save the image to. Just enter the Backup tab, and you can view this free backup software has checked the drives required for Windows to run. If you need to create a system disk image, enter the Source section to select all system partitions. Usually, we choose to create image files on the external drive. Step 3: Go back to the Backup interface, and click Back up Now button finally.
MiniTool ShadowMaker is helpful to restore your computer in case of unexpected disaster, which can avoid Volume Shadow Copy Service error 0x or 0x during system restore. How to do this job? I have run across several situations with XP machines where the command line for the SwPrv service is incorrect. On the top toolbar, click on View, Status or click the Status button on the toolbar. Next check the command line used for the SwPrv service. Navigate back to the top root folder.
Inside the Console Root folder, goto Services local. Notice the Path to Executable field. If it isn't, then this is what is preventing the service from starting.
It is obviously a good idea to export a backup reg file of the above key in case you make a mistake or need to restore the original settings. Locate the TypeLib registry value. If that is not the case, you have to delete the key, and then you have to recreate the key.
I have it installed and it works fine. As a guide to repairing Windows 7 without losing your data, have a look at these Vista articles as they will apply equally to Windows 7. Was this reply helpful? Yes No. Sorry this didn't help. Thanks for your feedback.
0コメント