Double-Take's eponymous flagship product was one of the first high-availability solutions for Windows providing asynchronous replication and failover even before Windows NT 4.0 hit the mainstream. Over the years, it has fine-tuned the data capture and replication core of the product while adding features to simplify the process of recovering common applications, making Double-Take Software the market leader for host-based replication.The problem with Double-Take and all its direct competitors such as CA WANSync, Neverfail, and SteelEye, is that you have to set up a recovery server, real or virtual, to take over for each server you're protecting. While this enables recovery times of a few minutes as the recovery server restarts with the personality of your Exchange or SQL Server, it can be an expensive way to support applications that have less demanding recovery time objectives.

Livewire leverages Double-Take's file system filter and replication engine while allowing you to use a single target server to protect multiple source servers. The trade-off is that Livewire uses a process more like restoring a server from backup than the automated server to server failover process used by Double-Take, so rather than taking 2-5 minutes to recover a server, Livewire will take somewhat longer. Exactly how much longer depends on how much data you have to copy from the target server to your recovery server.

Since Livewire uses Double-Take's real-time replication engine as its data source, recovered servers will come back with their data pretty much up-to-the-minute, depending, of course, on sufficient bandwidth for replication, where conventional backups bring back servers with significantly older data. It even supports VSS to provide multiple restore points and ensure database consistency, with up to 255 snapshots on the target server.

While you can restore your server to a virtual server or physical box with dissimilar hardware, Livewire, unlike true image backup solutions such as Symantec's Backup Exec System Recovery and UltraBac's UBDR Gold Livewire, doesn't do bare-metal restores. Instead, you install Windows on the target server and Livewire merges the drivers from that Windows install into the Windows from your source server. If you're restoring to a VMware Infrastructure host, it will work through Virtual Center to automatically provision a server from a template and then inject the source server into the new VM.

With a list price of $1,295 for each source or target server, Livewire costs significantly less than Double-Take even before the hardware savings from not needing a doppelganger for each of your source servers. From where I sit, it looks like a great solution for those applications that need RPOs better than traditional backups but aren't critical enough to need short RTOs.