At the recent VMworld we mentioned that VMware View 5 introduces PCoIP support for client-side image caching. In our VMworld presentation, we highlighted that, on average, this caching optimization reduces bandwidth consumption by about 30%. However, there are a number of important scenarios where the ability of the PCoIP image cache to capture spatial, as well as temporal, redundancy delivers even bigger benefits.
For instance, consider scrolling through a PDF document. As we scroll down, new content appears along the bottom edge of the window, and the oldest content disappears from the top edge. All the other content in the application window remains essentially constant, merely shifted upward. The PCoIP image cache is capable of detecting this spatial and temporal redundancy. As a result, for scrolling operations, the display information sent to the client device is primarily just a sequence of cache indices — delivering significant bandwidth savings.
This efficient scrolling has a couple of key benefits;
- On LAN networks, where bandwidth is relatively unconstrained, there’s sufficient bandwidth available for high quality scrolling even when client-side caching is disabled. In these situations, enabling client-side image caching delivers significant bandwidth savings – experimenting with a variety of different applications and content types (text heavy, image heavy etc), I'm seeing bandwidth reductions of over 4X (compared with caching disabled. mileage may vary, but I’m seeing this fairly consistently)!
- On WAN networks, where bandwidth is fairly scarce, when client-side caching is disabled, scrolling performance is often degraded to stay within the available bandwidth. In these situations, in addition to bandwidth reductions (which vary based on the degree to which scrolling performance is degraded when client-side caching is disabled), client-side caching also ensures smooth, highly responsive scrolling operations even in WAN environments with very constrained bandwidth.