NEC has been quietly selling its Express Cluster for Windows and Linux servers for more than 10 years while noiser competitors like Double-Take Software and CA XOsoft have gotten most of the attention. NEC's sold more than 10,000 copies of Express Cluster. Granted, some of that was in the Japanese home market, but it still put them in the top 5 in the market segment.Express Cluster comes in versions that provide clustering for shared disk SAN environments, synchronous or asynchronous LAN replication, or asynchronous WAN replication.

Today NEC's announcing a new release to support shared disk clusters in virtualized server environments. Where other vendors, like Double-Take and SteelEye Technology, are specifically supporting Hyper-V or VMWare, Express Cluster supports virtual server and virtual server host clusters running VMWare ESX, Xen, and Hyper-V, all for just $1,995/virtual server host. Express Cluster also has application support for SQL Server and Exchange 2007 and can replicate data from a shared disk cluster across the WAN to a third cluster member.

NEC's even hinting at features such as dynamic load balancing and cross hypervisor fail-over for a future version so a virtual machine on a failing Hyper-V host could come back up on an ESX host.