Virtual Machines Get Replicated

When it comes to disaster recovery, having a good data replication plan is crucial. Ask any of the IT managers who faced last year's disaster in New Orleans. But when it comes to server virtualization, the situation gets murky.

Replicating data on virtual servers from the likes of Microsoft and VMware can force users to install multiple servers to accommodate each instance of a virtual-server application (for instance, SQL Server, Exchange, etc.). Not all products can replicate virtual servers remotely. And user-friendly pricing packages that don't force users to pay for multiple copies of a replication package have been thin on the ground.

It's important to note that while several products today support data replication of virtual machines on a SAN, we're talking here about replicating from server to server. And so far, there have been few direct product fixes for the complications involved.

But several firms, including Datacore, NSI Software, and XOsoft are making headway. Next Monday, NSI Software will start shipping Double-Take for Virtual Systems, a product that replicates data from one Windows-based virtual server to another. Users have the option of replicating individual virtual machine applications like Exchange or SQL Server to one or more remote servers. Alternatively, they can replicate the entire virtual-machine server and enable failover in case of disaster.

NSI's Double-Take for Virtual Systems has been tested with Microsoft Virtual Server, VMware ESX Server, and VMware GSX Server. It costs $7,995 -- a price that supports licenses for five virtual servers.XOsoft has been supporting virtual-server replication with its WANSync and WANSyncHA products for two years, the vendor claims. The software also can replicate data from server to server per virtual machine as well as per server and works with not just Windows-based servers but with Sun Solaris AIX. Support for Linux is planned for April 2006.

XOsoft's products have been tested on the same trio of systems supported by Double-Take. The product, however, is still priced on a per-server basis: WANSync starts at $2,100 per server and WANSyncHA starts at $3,500 per server. That said, there are discounts according to the number of servers supported.

DataCore's SANmelody replication package supports server-to-server replication for MS and VMware servers, too, but the introduction appears to have been lost in the vendor's overall announcement of disaster recovery in January 2006. (See DataCore Tackles DR.)

SANmelody is priced from $8,000 to $15,000. The high end includes all software for two sides of the server network, local or remote, and runs with VMware ESX and GSX servers.

On the downside, there appears to be some confusion about how the latest virtual server replicators are priced. So far, DataCore appears to be the only vendor to offer a multi-license iteration of its replicator for virtual server use.And therein, NSI may have hit a nerve. At least one user, Praneeth Machettira, online technical director at Suffolk University Business School, says the pricing and simplicity of Double-Take distinguished it from XOsoft's package.

Machettira has spent a year porting his distance-learning application as well as SQL Server onto virtualized servers from VMware. So far, he figures he's saved $60,000 to $70,000 by porting the apps to roughly five virtual servers that address more than 350 remote and local networked desktops, which in turn serve over 2,000 students and faculty members in the school's online MBA program and other graduate courses.

While he liked XOsoft when making his evaluation last year, he prefered NSI's simpler approach. "It's not just about technical competence," he says. Double-Take was cheaper and easier for his tiny staff of less than ten to learn than he felt XOsoft's product would be.

Now NSI says the new multi-license pricing is part of its attempt to keep things simple for server-to-server virtual replication. Machettira's sold on that, too, and is in the process of installing it.

Mary Jander, Site Editor, Byte and SwitchOrganizations mentioned in this article: