Fragmentation and the Virtual Revolution

It hasn’t been all that long since virtual servers came on the scene, allowing entire machines to operate as software applications. This technology meant that companies hanging onto only partially used hardware servers—and sweating over the expensive space and energy they were taking up—could consolidate them as virtual servers and fully utilize machines. Virtualization has certainly meant a revolution for data centers.

But as one might expect, the revolution has not stopped with servers. Now companies are looking at how they might virtualize the scores of desktops scattered throughout an enterprise, again reducing hardware and energy consumption and simplifying management as well. The PC monitors remain with users, but become very similar to terminals connected to virtual PCs that could be located anywhere, including a company’s main data center.

It might seem that since a machine is virtual, it would not suffer from a traditional issue such as fragmentation. After all, if a machine is existing as purely data in memory, how can file fragmentation be a problem?

The answer is that the data being utilized by a virtual machine is still being saved on a hard drive. A single drive or set of drives is supporting a number of virtual machines—called “guest systems”—and data from all of those machines is saved on the drive or set of drives on what is called the “host system.” File fragmentation, which drastically slows down performance on any drive, has an even worse effect in virtual server environments. Note that fragmentation will occur no matter what is being “virtualized”—servers, PCs or even in the future, networks.

Since a virtual machine has its own I/O request which is relayed to the host system, multiple I/O requests are occurring for each file request—minimally, one request for the guest system, then another for the host system. When files are split into hundreds or thousands of fragments (not at all uncommon) it means the generation of multiple I/O requests for each fragment of every file. This action is multiplied by the number of virtual machines resident on any host server, and doing the math it can be easily seen that the result is seriously degraded performance.

Defrag is obviously crucial for virtual machines—but it must be the right defrag technology. A fully automatic defrag solution means that files stored at the hardware layer are consistently and automatically defragmented, and fragmentation is never an issue at all. Only idle resources are utilized to defragment, which means that users never experience a negative performance impact, and scheduling is never required. Virtual machine performance and reliability are constantly maximized.

Virtualization means the sky is the limit for enterprises today. Don’t let fragmentation keep you tied to the ground.