Friday, November 02, 2007


Virtualization is either a buzzword you use at work or its about to be (link to another article). At the end of the last century a small company, VMWare, started producing a software package, also named VMWare, that allowed you to use a single server to act like multiple servers. This may seem like a ridiculous concept because if you are used to how slowly your computer runs it seems counterintuitive that you'd gain anything from making your computer work for two, three or four people all at the same time. The catch, however, is that with servers the full processing cycles are not in constant use. Server computers tend to have a higher caliber processor and sometimes they have multiple processors, more robust internal structure and faster drives. Being able to divide all the processing power of those machines between multiple programs or teams simply means a more full usage of those resources as well as less administrative overhead to support the same number of teams (four development teams using a single piece of hardware as oppossed to each having their own hardware). When considering servers you can often hear terms such as load, load-balancing, fail-over, utilization. These terms refer to how much a server is used and how it can pass along some of its work to other servers if it gets too busy.

Virtualizing multiple instances of the OS on a server means better resource utilization (as long as the server can handle the load). Companies like VMWare (purchased by EMC2), Microsoft (producers of Virtual PC) and SWsoft (makers of Virtuozzo) make software that allow users to create virtual servers that are hosted on a single server.

This technology is relatively young but still tried and a solid performer for businesses. Virtualizing servers has a positive payback for most implementations.

Newer on the scene, however, is the concept of storage virtualization. This concept seems so recent that there is little evidence that it resolves as many issues as it introduces. Some of the benefits are freedom from resource management at the user level; users don't have to remember that the H: drive has 120Gb and the J: drive only has 4Mb available. With storage virtualization a wrapper overlays the storage layer and makes it addressable to the client as a single entity. Users theoretically just connect to the virtual storage repository and their data is stored for them by the wrapper. Another benefit of storage virtualization is that files gain some resiliency to hardware failure and hardware appears to be hot-swappable beneath the virtualized wrapper.

Virtualized storage is different from SANs, NAS and, although it shares some characteristics with CAS, it is a different creature from CAS as well.

Network World "Vendor claims about storage virtualization flawed"
Enterprise Systems "Next-Generation Storage: Think Virtual (2005)"


Lee Parker said...

Comes around, goes around.

KevinRiggs said...

Lee, true enough. My intent was to contrast the commodity that virtualized servers have become in terms of memory and processor resources with the relatively newer LUN masking that companies like ESG (EMC subsidiary) are focusing on. While virtualization has been around in many formats its getting more "buzz worthy" and knowing the difference in a VMWare/VirtualPC/Virtuozzo type of virtualization and what happens when storage space is virtualized in a larger environment seems like a distinction to bring up.

Thanks for your comment and especially the link; I like knowing the background.