When the Windows operating system generates disk IO, it optimizes that IO so that data is read from and written to disk sequentially so that it can maximize overall system performance. In VDI environments there is no direct connection between the desktop operating system and any physical disk (with local or shared storage). Therefore, the disks are shared amongst other guest operating systems, so the Microsoft Windows operating system assumption of exclusivity is no longer valid. As a result, the hypervisor converts sequential IO into random IO (the IO Blender effect) that decreases storage and desktop performance and in turn reduces the effectiveness of any available storage cache modules. With desktop virtualization, the IO blender effect is more pronounced due to the fact that the number of desktops per physical server is much higher than server virtualization.

From Random To Sequential IO

Atlantis ILIO converts the small block random IO generated by the hypervisor into larger blocks of sequential IO to send to storage, increasing storage and desktop performance, and maximizing the opportunity to deliver all requested data locally from memory.