Application-aware Backups in the virtual world!
Many of today’s backup vendors are advertising that they can do application-aware backups. That’s great – but what does that exactly mean? Why would this be of any value to me and how will it help my organization? The answers to these questions are pretty straightforward and the added value to having application-aware backups can become invaluable!
Let’s start with, “What exactly are application-aware backups“?
Application aware backups provide added intelligence to interact with applications that reside on a server. This server can either be virtual or physical but for the purpose of this blog post we will focus on virtual. These applications could range from your enterprise software solutions all the way down to your small homegrown applications. The key here is the ability to interact with Microsoft’s Volume Shadow Service (VSS) so that it can be treated properly. In other words, application-aware basically is saying that we will be doing a transactionally consistant backup of applications such as SQL, Exchange, Active Directory, Sharepoint, and I’m sure many more could be added to the list here. The key for application-aware is really tied to the ability to tap into the vss writers.
If you run this command, you will have a sense for which applications are covered by being vss-aware.
vssadmin list writers
So what happens when we trigger these VSS Writers?
The triggering of VSS writers will start a VSS freeze, the backup solution will find out if there is a VSS-aware application running inside a VM. It then requests Microsoft VSS to create a consistent and reliable view of application data prior to taking a VM snapshot. Windows VSS interfaces with VSS-aware applications and Windows OS to quiesce all I/O at a specific point in time. This way, it ensures that there are no unfinished database transactions or incomplete application files during data copying operations.
What happens if I don’t backup in an application aware manner?
This method would be called crash-consistent and for most servers that don’t rely upon a database, it would suffice. Any server that has a vss-aware application residing on it will almost always prefer to be application consistent. One example, when you restore a domain controller that has been backed up in a crash consistent manner, the server feels as if it has experienced a hard shut down and then continues on to do an active directory repair. And for Microsoft SQL, you may need to know how to replay logs into a database file.
As you can see, not quiescing these applications/databases can leave room for data corruption and/or lost data. Protecting your systems in an application aware manner will ensure that all data residing on the virtual machine is protected and will be accessible upon a restore. Another great reason for application aware backups is the amount of time and frustration that it could save you by enabling this capability!
Enabling this feature within Veeam!
When creating a new backup job within Veeam, all that you need to do is hit the check box for Application Aware Image Processing followed by credentials and you’re off and running!
*Update* One extra benefit that I forgot to mention was Veeam’s ability to do log pruning for Exchange & SQL. The fact that Veeam is the only vendor that can do this at a image-level backup is extraordinary! See below on where to enable! <– Thanks Doug Hazelman, @VMDoug!