In-Depth

The Importance of Being Clustered

Sanbolic's chairman Bill Stevenson sees clustered file systems as a key technical piece in the virtualization puzzle.

• By Ed Scannell
• 05/01/2008

Sanbolic Executive Chairman Bill Stevenson

Bill Stevenson, executive chairman of Sanbolic Inc., appears to be in an enviable spot in the burgeoning virtualization market. His company has possession of an enterprise-class clustered file system called Melio, which is a crucial ingredient in improving performance and availability in virtual server environments. This is a key technology piece missing from Microsoft's Windows Server 2008, which doesn't figure to be present for the foreseeable future. The company has worked closely with both Microsoft and Citrix Systems Inc. on crafting virtual server migration solutions, as well as clustered storage solutions.

Stevenson, an instrument-rated pilot and Fulbright Scholar, sat down with Redmond Editor Ed Scannell to discuss Sanbolic's clustered file system, evaluate the technical merits of competitors such as VMware Inc., Citrix and Microsoft, and offer some hints about the latter's interest in acquiring a certain clustered file system.

Redmond: Why is a clustered file system so important in the world of virtualization?
Stevenson: VMware has made that easy for us to answer. Their product suite has three components: a management layer, a server-partitioning layer -- or hypervisor -- and one that is the VMS clustered file system. It plays an important role in that it lets multiple and physical host servers have access to all of the virtual machine images concurrently.

This is what enables them to migrate a virtual machine from one physical host to another. For many customers, that migration capability is important because it gives them high-availability capability. They can move an application from one server to another for maintenance or in the event of a hardware problem. It also gives them great flexibility because they can more easily load balance how they put applications on the physical hardware that's virtualized. This is what we're doing with Melio.

Why do you think Microsoft has yet to deliver this for Hyper-V?
I can't speak for Microsoft, but a clustered file system is a very complex piece of software. Microsoft has been working to close the gap with VMware. I don't know if they're resource constrained or if it's something else, but it's not something that can be developed quickly.

What are some of the major differences between your file system, Melio, and VMware's offering?
Well, [VMware's offering] only works in VMware's virtualization suite. You can't use it on physical hardware for any other OS. Our file system was designed as an enterprise file system for physical servers, so it can be used for applications running on physical servers with no virtualization involved. It can also be used to enable and simplify the migration of virtual machines. We're seeing users have a greater interest in not having a separation of physical and virtual environments, but having both running with the flexibility to move across either of them.

We also have a more complete feature set than VMware because our feature set is designed as a general- purpose file system; there are no effective limits on file size or volume size. We have concurrent read/write access, but VMware has a coarse-locking mechanism so it can't support applications having concurrent read/write access to the file system.

The biggest opportunity to date for virtualization has been server consolidation. Is desktop application virtualization the next hot area?
We see both being big opportunities. The penetration numbers for servers are less than 10 percent, and clearly users have seen tremendous benefits in cost- and energy-reduction to date. Desktop virtualization is just getting started, but there's tremendous value to that in enterprises in terms of significantly reducing management costs and improving security for desktop users.

Why is virtual machine migration so important these days?
If you consolidate your servers down from 10 to one physical server, it cuts down the management and number of physical machines by a factor of 10. The flip side of that is by consolidating down apps from 10 [machines] to one, if that machine fails it would be 10 apps affected, not just one.

But users are interested in the flexibility of a virtualization layer that allows them to have an application not be tied to a specific piece of hardware, as well as the flexibility to migrate that application across hardware for both availability and load balancing. It becomes a key driver of the economics and the availability of the data center that's propelling this move toward virtualization.

Do you think virtualization is going to eliminate more jobs than it creates over the long term?
It will change the jobs that are out there. The focus initially for virtualization has been cost reduction, and that implies fewer servers and perhaps fewer people. But the real benefit for virtualization is the ability to bring new business initiatives online quickly. I think it's likely to create a lot of jobs going forward, and a lot of interesting high-value jobs at that.

What can we expect to see from Microsoft and Sanbolic in the way of a licensing deal or acquisition?
Right now we're marketing partners going after several application areas together. Going forward we see the virtualization market as an important area of growth for Microsoft, so we've been spending a lot of time in Redmond. We don't have any formal deals to announce publicly, but we're helping them build their business and that's a mutual growth opportunity for us both. How it develops will hopefully be an interesting story in the next year or so.