Barracuda Networks Product Blog

Posted by: Andy Jensen, product manager

As we roll out of Barracuda Backup Service v. 4.1 to our customer base, I’d like to discuss some of the advantages offered by features new to this release.  In my last post, I discussed Bare Metal Recovery.  Today I’ll cover our use of USN Journaling to provide Continuous Data Protection.

The Barracuda Backup Service has included change detection intelligence since the inception of the product.  Change detection is critical because it is minimizes resources needed to perform a backup.  A typical image-based backup solution sees all data on a volume as a single chunk.  Each time a backup runs, a snapshot is created, pulled across the network, and written to disk.  Depending on the solution, that data may then be deduplicated and/or compressed after it has been stored.  The Barracuda Backup approach is different. It is file based rather than image based and it only backs up data that it has not seen previously or data that has changed since last time a backup ran.  After the initial backup, rather than transferring all the data on a volume each time a backup runs, the Barracuda Backup server only has to move the incremental changes to your data set.  File data is then deduplicated before it is written to the backup server.  This shortens backup windows, reduces load on LAN resources, and reduces the amount of hard drive space needed to store backup data.

Some History

Early versions of the Barracuda Backup Service controlled this process from the server itself.  When a backup ran, the Backup server would communicate with the target device, remotely walking the file system looking for changed data, and requesting anything that had changed.  This procedure was good in fairly standard environments, but when a customer had an unusually large number of files, there was a lot of overhead involved in touching each file across their network to check for changes.  This meant backup windows remained lengthy even if not a lot of data had changed.

When we introduced the Barracuda Backup Agent software for Microsoft Windows, we made a change to speed up this process.  The backup agent included a database that kept track of what had been sent to the backup server.  By keeping track of changes on the server that was being backed up, we eliminated the need walk the file system from across the LAN (All of those queries are local); but that was not quite enough.  On servers with large numbers of files, sometimes millions of small files, backup windows were still unnecessarily long due to the need to walk the file system before backing up data.  Even with the local windows server doing all the work, touching every one of millions of files can be a lengthy process.

The Solution

The solution we have deployed in Barracuda Backup Service v. 4.1 takes advantage of a feature in Windows called the USN (Update Sequence Number) Journal.  Quite simply, it is a log of changes that have been made on the server being backed up.  Once the initial backup runs, the Agent can get information about files that have been changed, modified, or deleted from the record kept in the journal.  By monitoring those changes in a log, it isn’t necessary to check every file when a backup runs, it is only necessary to address what has changed.  This dramatically reduces the amount of time it takes to perform backups and reduces the overall load on the server being backed up.  Especially in those scenarios where millions of files need to be protected, tracking changes as they occur over time is far less system intensive than checking every file for changes when a backup runs.

The combination of extraordinarily short backup windows and minimal use of system resources means that customers can back up file system data quite frequently.  This technology is the basis for what is called continuous data protection or CDP.  Continuous data protection allows customers to run backups during the day while their data is changing.  Barracuda customers leveraging this new feature have found value in the ability to complete backups of their critical file system data as often as every 15 minutes.

We are very excited about offering this technology that is going to have a tremendous impact and reduce backup windows for all of our customers.

Barracuda Backup Service v 4.1 is available immediately to all customers. For more details on the Barracuda Backup Service please visit: http://www.barracudanetworks.com/ns/products/backup_overview.php or call 1-888-ANTI-SPAM to speak to one of our specialists.