StorMagic Storage Virtualization
By: Andrew West, CTO
Not too long ago, you had to invest a significant amount of cash into a shared storage subsystem (aka a SAN – Storage Area Network) to realize all of the benefits of server virtualization. In the case of VMware’s latest version, vSphere, one of the most important benefits is arguably the ability to move a virtualized server between different physical servers/hosts (vMotion) whenever you want to without anyone knowing that it’s happening. This feature is extremely popular since it affords Network Administrators the ability to upgrade and maintain physical host severs and the hypervisor software running on them during normal operating hours, rather than following the traditional routine of waiting until the close of business and spending precious personal and family time to do so in order to avoid inconvenience for the employees and lost productivity and revenue for the organization. Other features of vSphere that require a SAN include High Availability (HA) and DRS (Dynamic Resource Scheduling).
Before we partnered with StorMagic several months ago, we didn’t have any low-cost server virtualization solutions to offer our smaller – and typically more cost-concious – clients. Now we do with StorMagic’s svSAN. Just as vSphere virtualizes servers, svSAN virtualizes Direct Attached Storage (DAS) on any server running VMware ESX, including the latest version, vSphere. Instead of buying a separate SAN, we include more storage in the host servers; svSAN then virtualizes that storage and makes it available for use by any host server over the network. For example, if I have two hosts (let’s call them hosts A and B) running vSphere and I load svSAN on host A, I can run virtuals servers on both hosts that utilize the virtualized storage on host A, and therefore I would be able to vMotion virtual machines between both hosts at will. In short, I’ve created a virtual SAN using the local disks in host A that is shared between both host A and B.
So, all this sounds great, but I know you’re thinking about what happens when host A fails. Maybe the disk controller fails, maybe the power supplies fail, or maybe someone trips over the network cable attached to the physical server . . . all of my eggs (read virtual servers) are now in one basket, and we all know that that’s not a good thing for redundancy. Enter the second impressive feature of svSAN – High Availability (HA), not to be confused with the HA feature of vSphere. With svSAN and the HA license loaded on both hosts (which are configured with the same amount of local hard disk storage, of course), you now have a virtual SAN in a bi-directional RAID 1 configuration in which either side of the mirror can be written to with all changes being written to the other side of the mirror. All of you gear heads out there know exactly what I’m talking about, but for those that don’t, this means that either server can fail, but all of my virtual servers will still be available.
This is, in fact, the configuration we recommended for our smaller clients – two identically configured servers with lots of hard disks running svSAN with HA. With this solution, host maintenance is a piece of cake and doesn’t require any down time, and all of your servers will be redundant as long as they are virtualized. And, of course, the cost to do all this is very reasonable.
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