Virtualization is fundamentally a great idea. And virtualization technologies have never been better. But the ability to effectively share resources in virtual environments runs into several barriers, particularly this one: There are I/O bottlenecks created and performance degradations that result due to the accelerated fragmentation that occurs in virtual platforms.

This factor is exaggerated by copy-on-write technologies like snapshots, replication, and inline de-duplication. These technologies are designed to make copies of each and every write, at block level, that occurs on a disk/volume/virtual disk. It particularly applies to special virtual disk types such as VMware’s Linked Clones and Microsoft’s Differencing Disks that use copy-on-write technology.

Here’s why:

When a file is broken up to write it to scattered locations on the disk, the increased write and read time required to address the scattered file pieces causes reduced performance. Running a process to handle this after the fact, in a copy-on-write environment, can also make more work for the copy-on-write features and further impact I/O performance. Recently, Diskeeper Corporation created a new technology called IntelliWrite fragmentation prevention that assists virtualization by preventing up to 85% of all fragmentation before it occurs. IntelliWrite is a feature of Diskeeper Corporation’s new optimization product for virtualized environments, V-locity 2 virtual platform disk optimizer. It minimizes unnecessary I/Os passed from the operating system to the disk subsystem, topping all previous standards for I/O performance and reliability.

To optimize the advantages of special virtual disk types such as VMware's Linked Clones and Microsoft's Differencing Disks, another V-locity feature comes into play: virtual disk intelligence automatically detects the special disk types and optimizes their capabilities by creating a state as close to zero fragmentation as possible.

The virtual disk intelligence of V-locity 2.0 and the preventative technology of IntelliWrite would result in superior I/O performance for users of these special disks.