Providers of host-based data replication are claiming to support VMware's virtual environment. But it's important, sources say, to probe exactly what that means.
Vendors such as CA, Double-Take, Neverfail, SteelEye, and Symantec all boast support for VMware virtualization. (See Double-Take Protects VMware.) But not all products are created equal, and the kind of support a replication package offers can determine how efficiently your network operates, how quickly you can recover from a hardware failure, and how much you'll spend to reach your goals.
Some products replicate VMware virtual machines on a one-to-one basis, while others can replicate the entire ESX server that the virtual machines run on. The kind of approach you deploy will determine how much you spend.
Double-Take, for instance, says the latest Double-Take for VMware Infrastructure can back up an entire VMware server without the licensing fees associated with multiple virtual machines. Similarly, SteelEye plans to announce support in March for ESX Console replication, so that firms can replicate entire servers (and save licensing costs as in Double-Take's case) as well as replicating data within and among individual VMs.
But there are tradeoffs with these products. Double-Take's VMware product doesn't yet have the byte-level replication that Double-Take offers in its regular replication packages. And because SteelEye deploys SCSI commands in dealing with links between hosts and shared storage, it's important to ascertain that the software works with other vendors' host-based packages designed to control multi-path links between servers and shared storage. (Got that?)