File Access Manager vs Volume Shadow Copy (VSS)

VSS provides a backup and recovery infrastructure for the Windows Server 2003 operating system only. It includes a mechanism for creating point-in-time copies of data. While the Service can provide coverage for some missed files during backups, there are several limitations, because most applications are either non-VSS aware or IT administrators are using VSS to backup “file servers” (VSS does not work with applications that install and saves files on different networked servers).

The advantage that FAM provides is that it can backup any file from any application in a consistent state, even if the data from the application is not VSS aware. Furthermore, FAM works on all computers starting with windows 2000 and up and is network ready. FAM runs silently and does not require that the application or backup program be aware of it.

Here is an example of how VSS works with a backup application:

1. The backup application is run
2. The backup application sends a command to VSS to take a snapshot.
3. VSS communicates with the application to finish existing transactions and pause new transactions.
4. VSS communicates with the storage snapshot technology (provider) to create a snapshot.
5. The provider creates a snapshot of the volume set.
6. VSS communicates with the application to resume normal operations.
7. The backup software copies the snapshot creating a backup of the volume set. Since the snapshot is not being accessed by any other application, all files on the volume will appear as closed and available to the backup software even though application programs are accessing the files on the original volume.
8. Upon completion of the backup, the requestor communicates with VSS to delete the snapshot.

There are several limitations with VSS in the above scenario:

The application that has the data file must be VSS aware
The backup software that wants to backup the file must be VSS aware
Applications that are not built specifically with VSS technology won't be able to have their data files backed up
VSS cannot predict or control the I/O flow of such legacy applications
VSS will need to pause business operations while it makes the snapshot
VSS only guarantees file system integrity and does not guarantee legacy writer transaction integrity
VSS is hard to setup properly
VSS is only supported on NTFS drives
Volume space for shadow copies must be specified. If the volume space is exceeded, then no shadow copy is created and the volume backup fails
No support for file servers. VSS is designed to manage data on machines where both the application and its related files reside. In a networked environment, where a file and the associated application both reside on different machines, VSS is not supported

The safe bet is to use File Access Manager as none of the above limitations are present.

With File Access Manager:

You can ensure that all the files no matter what operating system you are using will be backed up (Windows 2000 and up)
You can ensure data consistency with FAM’s advanced caching methods
You can ensure that no matter what backup software you use, the data will be backed up
You can ensure that all of your legacy and proprietary application's data files will still be backed up
You can ensure that the machines that you backup will not be interrupted while a copy of the data is being backed up
FAM is extremely easy to setup and works out of the box
FAM works with all file systems whether you are running NTFS, FAT32, or anything else
No volume space needs to be specified. In fact, FAM only uses the space needed for the changes of the file that is being backed up
FAM was built with a networked environment in mind. Install FAM on any workstation/server on your network and your backup software will be able to access its locked and open files