If you need to recover a file that's been deleted, you obviously can't right-click
the file in the shared folder and select its properties. In this case, you need
to work at the folder level. Instead of connecting to the UNC path \\Uptowndc\Sales,
you'd connect to the administrative share of the C drive (which is where the
Sales folder resides): \\Uptowndc\C$. Right-click the Sales folder, select Properties,
and click the appropriate button to view, copy, or restore the entire contents
of the folder. If you're interested in only one file, copy the folder to a new
location, then right-click the file and work with that file's previous versions.
Vista and Shadow Copies
Vista is the first desktop OS with built-in shadow copy capabilities. In Vista,
shadow copies are part of System Restore and are called restore points.
Restore points are enabled by default for the C volume, so right out of the
gate you get shadow copies of your files daily, as long as the volume has at
least 300MB of free space.
The default scheduled task that creates restore points is called SR, and it
runs only when the computer has been idle for 10 minutes or more and is on AC
power. If for some reason the SR task fails to run at its scheduled time, it
will run as soon as possible. You can also enable restore points for other volumes
if you choose. Vista uses up to 15 percent of available hard disk space for
storing restore points.
To configure and manage restore points, click the Start orb and right-click
Computer, then choose Properties; on the Tasks menu select System protection.
Accessing System protection requires administrative privileges, so when
prompted by the User Account Control UI, choose Continue.
On the System Protection tab of the System Properties page, which Figure
3 shows, you can manually create a one-time restore point by selecting the
volume and clicking Create, naming the restore point, and clicking Create
again. The process can take a few minutes, depending on the size of your volume,
but when it's finished you get a message confirming success. If you choose to
enable automatic restore points for a volume, Vista creates a new restore point
for that volume every day and at system startup time.
Accessing previous versions of files and folders on Vista is performed in the
same manner as accessing them through a shared folder on Windows 2003 from a
client that has the Previous Versions Client application installed. But Vista
lets you access the previous versions of files and folders locally. Simply open
Windows Explorer, right-click the file or folder you want, select Properties,
then click the Previous Versions tab, which Figure
4 shows. The options are the same on Vista as they are for the earlier Previous
Versions Client, and they work the same way.
VSS and SANs
Another cool feature of VSS on Windows Server 2003 Enterprise Edition and Datacenter
Edition is the ability to quickly and easily copy and move data on a SAN. VSS
can create a shadow copy of a multi-terabyte volume that you can then export
from a SAN and import to a server in a matter of minutes, thereby transferring
a large amount of data very quickly. Every storage vendor sets up this capability
differently, so contact your vendor for details.
VSS Configuration
For volumes with VSS enabled, I recommend you configure 16KB or larger
cluster sizes. VSS tracks changes to files in 16KB blocks. On volumes that are
from 2GB to 2TB in size, 4KB is the default cluster size. But on clusters smaller
than 16KB, the VSS provider can't determine whether a file has been defragmented
or changed. So VSS treats a defragmented file as it does a changed file—it
generates a new shadow copy of the file. After defragmentation of a disk
that has small clusters, VSS might cause the shadow copy cache to grow very
quickly and overwrite all existing shadow copies. (For more information, see
the Microsoft article "Shadow copies may be lost when you defragment a volume"
at http://support.microsoft.com/kb/312067.)
To find the cluster size on a volume, you can use the Fsutil command. For example,
to find the cluster size for volume C, you'd type the following at a command
prompt:
fsutil fsinfo ntfsinfo C:
If your cluster size is smaller than 16KB and you want to increase it, you
need to back up your data, reformat the volume with a larger cluster size, then
restore your data. Be aware that NTFS compression works only with 4KB cluster
sizes, so you might need to decide whether compression or VSS is more important
in your environment.
How NTBackup and VSS Work Together
In the past, if a file was open or locked by a service or application while
a backup was being performed, the locked or open file wasn't backed up, causing
problems when administrators needed to restore that file. Data consistency is
paramount when it comes to applications that require many files to be open at
the same time, such as databases. When multiple files are open during a backup,
it's possible that between the time that the first and last file is backed up,
changes might have occurred in the last file. So when the database is restored,
the data is no longer in a consistent state.
Windows 2003's backup utility, NTBackup, uses VSS to ensure that backups are
consistent and complete. VSS works in conjunction with a piece of code, called
a writer, from a file's application. A writer protects the application's
data and provides information such as the location of the data and the backup
and restore methods available. Applications that don't contain a writer are
not VSS aware. Administrators need to know whether their applications are VSS-aware.
In a worst-case scenario, an administrator might try to restore an important
file and discover it's not even there—it never got backed up because
the application wasn't VSS aware. Windows 2003 includes writers for AD and NTFS.
To find all available writers on a server, type the following at a command prompt:
vssadmin list writers
When you run NTBackup in Windows 2003, the utility requests a list of all writers
that VSS is aware of. VSS not only lists the writers, but also provides all
known metadata about the writers, such as each writer's backup and restore methods.
VSS uses the metadata to determine which applications support shadow copies.
When NTBackup asks VSS to create a shadow copy, VSS sends a message to the known
writers to freeze all data writes, create a shadow copy, and store it in a difference
file. A difference file keeps track of what has changed or is different
since the last shadow copy was created. Then VSS lets the writer continue its
write operations. The backup is performed using the data in the difference file.
Tobias Schmidt June 15, 2007 (Article Rating: