Anyone knows any good continuous backup software? I'm using Sonicwall appliances but I want to know if there are any good software solution for this.

Update 1: I'm referring to filesystem. Of course, any other tool like Oracle and so on have their own method.

Update 2: The sonicwall appliance looks continually for filesystem changes and archive them, also saves versions. This appliance is not working fine, a lot of bugs and no way to get nice support...

  • 1
    Can you clarify with what you're trying to back up? There's different solutions for Windows, SQL Server, Exchange, Oracle, etc.
    – Brent Ozar
    May 30, 2009 at 12:49

8 Answers 8


Are you after a backup system (where you can recover previous version of files) or merely replication?

A few products come to mind:

  • Veritas Volume Replicator has the ability to replicate filesystems
  • Windows Volume Shadow Copies can be used for backups
  • Windows DFS can be used for replication
  • NetApp file servers can do both replication, and replication as a backup mechanism
  • ZFS filesystems can easily be replicated
  • Backup software companies like Bakbone and Symantec (among others), I'm sure) are able to do continuous live backups
  • rsync and related tools such as rsnapshot can do close to continuous depending on the requirements

On the consumer side of things, but also applicable for business, you'll find plenty of startups with new nifty cloud enabled tools that fit in the replication/backup realm:

I'm probably missing plenty more... Hope this helps!


Have a look at DoubleTake. They got what you need if you can afford it.


If you're running in a Windows environment, then two products to look at are:

  • Microsoft System Center Data Protection Manager (DPM)
  • Symantec Backup Exec with Continuous Protection Server

Personally I prefer to use Microsoft products on Microsoft operating systems, and DPM can take backups as frequently as every 15 minutes, which is not actually continuous protection but close enough for most realistic situations.

DPM has a very clever single-instance storage implementation which works at the cluster level. It also knows how to correctly handle backups of exchange and SQL. DPM uses volume shadow copy to creat its snapshots so open/locked files don't present any problems.


If you are willing to use a snapshot system rather than true continuous backup, take a look at Solaris with zfs snapshots. A good tool to use with this to actually take backups is Zetaback - available from labs.omniti.com/trac/zetaback . (not linked because the evil system won't let me)


What you need is a log structured filesystem. Given such a beast, you can stream changes to a backup server for a duplicate copy.

The downside is that this can be really damn slow. Recovery from backup is usually an important consideration and it is a fact that continuous backups have to store more potential states to back up to. Searching to find the one you want may cause pain.


I would suggest you look at ShadowProtect Server. This is a great backup solution that will do snapshot based backup while not actually continuous you can setup the backup interval to something like 15 or 30 min. This is a much better solution than the Sonicwall product which I have also looked into deploying.

Also if you are using Windows Servers 2003 could look into using shadow volumes copy service.


I'm not sure how practical this suggestion is (well, I am, it's not!), but DragonFlyBSD's HAMMER filesystem can create snapshots of your data every 30secs continually. There's a very similar Linux filesystem being developed too: btrfs.


If you want to setup a server I can recommend http://www.dirvish.org/ you can define when to do backups, so you could define like every 15 min ie to be almost continuous.

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