Why pay $1,500 per virtual desktop, if you can have a physical machine of the same performance-level at half the cost. While the functional and maintenance advantages of virtual desktop computing are evident, the per machine CAPEX often is the key stumbling block for this type of project. It is very hard to convince your CFO to write a check for more money per virtual machine than it would cost to acquire physical desktops.
Storage cost often constitutes 60%-70% of the overall price tag of your VDI project. Common SANs are not made for supporting large numbers of individual desktop operating systems, due to performance constraints of spindle-based drives. To increase SAN performance, we have to add more physical disks, and ultimately additional SAN units. Alternatively, we could add SSD-based SAN accelerators. However, SAN accelerators are expensive and only of limited effectiveness when it comes to ensure quality of service for virtual desktop images.
Wouldn't it make much more sense to increase performance without unnecessarily adding more expensive disks, with all the CAPEX and OPEX attached? Atlantis Computing offers a very interesting solution to the VDI storage conundrum. The Atlantis ILIO virtual appliance, in combination with Cisco Systems' Extended Memory Technology, supports so-called diskless VDI. Atlantis ILIO processes all NTFS traffic and performs inline de-duplication -slimming down the individual desktop image by up to 90%. Then all desktops are placed exclusively into server RAM, which leads to extremely fast response times.
In addition to deploying the Atlantis ILIO virtual appliance, there is one other ingredient needed to cost-efficiently run virtual desktops from memory: Cisco's Extended Memory Technology. This technology quadruples the amount of memory that can be accessed by each CPU slot, delivering up to 384GB of RAM to a dual socket server, at full bus speed (1333Mhz).
Atlantis ILIO hosted on a Cisco UCS C250 M2 with an Intel 5670 12 Cores and 384GB of RAM achieves a stunning 44,123 IOPS (based on company-internal benchmarks). Hosting 120 virtual desktops on this setup allocates over 360 IOPS to each virtual machine at a per machine cost of about $200.
Do we really need 360 IOPS per vm? Of course not, but who has ever complained about 12 second boot up times? All in all, Atlantis ILIO in combination with Cisco UCS is a clever solution to the VDI storage performance bottleneck.