VSS snapshots and how it affects your backups
A key component of backing up Windows based servers and desktops is the Volume Shadow Copy Service (or VSS for short) that allows for a VSS snapshots to occur.
What is a VSS snapshot?
Just as the term snapshot means in photography, the same analogy can be used with computers by creating a ‘snapshot’ of an entire machine, specific volumes or even just individual files as they were at a specific point in time.
In short, VSS gives the ability to copy data (even if it’s currently in use) by applications which utilize the technology.
VSS consistent application backups
Applications such as Hyper-V, Microsoft Exchange or Microsoft SQL – the files are generally in use as guest machines are still serving the network, e-mail is still sent and received and data is still being committed to memory and databases. Basically; they’re unable to have interruptions or the result could be major corruption (and data loss).
It’s the equivalent of having the power cut off unexpectedly.
This is where VSS comes in handy as it allows for the backup process to read the contents of the snapshot and commit the application data. An application-consistent backup is one that informs the application that a backup is about to take place and allows the application to flush and pending I/O operations to disk. As a result; creating a state of consistency which the backup can use without the possibility of data corruption or lost data.
The way which VSS does this is by using the VSS writer related directly to the application. You can discover if an application contains VSS support. Run the following command in an elevated command prompt window and look for a writer that is related to it directly:
vssadmin list writers
Many backup vendors utilize the VSS snapshot service…
As Microsoft have provided VSS since Server 2003 on all operating systems and it allows the backup process to read the snapshot data and send it to secondary and tertiary storage; many backup vendors use the API’s to perform backups.
In addition; a small list of these vendors are:
Help with VSS snapshot problems
Since the majority of common backup solutions utilize VSS, it’s not unheard of errors occurring due to VSS. These can sometimes be difficult to pin down.
As a result; TestMyBackups is able to help as we’ve had years of experience resolving all problems VSS snapshot related.
Have you experienced issues with VSS during backup? Comment below, or let us help.