During VMworld I attended a good session on VDI (virtual desktop infrastructure) for remote users, presented by HP. To support ROBOs (remote office/branch office) there are two basic architectures.
The first is a centralized approach, where one or two datacenters host all the required servers and storage to support all VDI users. This is great for centralized administration, protecting data inside the datacenter, and minizing costs by pooling servers and storage. However, users are then dependent on the WAN and bandwidth/latency/jitter are can be big factors. If the ROBO has POS (point of sale) or other critial users, it’s totally unacceptable to be dependent on the WAN. In addition, existing VDI technology is generally not as robust across the WAN and has limited support for 3D graphics, video, CAD/CAM, etc.
The second approach is a distributed model where each ROBO has their own self-sufficient set of servers and storage, which is not dependent on the WAN. One major barrier to this deployment is the cost of shared storage if you want to use any of the HA features of ESX such as vMotion, HA, FA, DRS, DPM, etc. Even a small 10TB iSCSI array can cost $35K or more, which is not cost effective to support a handful of users.
To address the shared storage cost, the speaker presented a novel idea. HP’s Lefthand iSCSi array can be purchased as a virtual appliance. List price for the virtual appliance is less than $5K. What is the Lefthand iSCSI VSA? It’s a VM which runs on top of ESX and turns local non-shared disk storage into shared iSCSI storage. You can cluster the VSAs across multiple physical hosts for increased performance and redundancy. Lefthand is also compatible with ESX SRM, and supports WAN data replication, snapshots, and thin provisioning.
With this architecture, a small ROBO could have two or three ESX hosts, clustered VSAs, and fully support vMotion, HA, FT, DRS, and DPM for all VDI users. For disaster recovery, you could also implement SRM.
For small remote offices, this approach could be very appealing and really cut down on the cost per user of VDI. Since the VDI servers are local to the user, you would get the best performance and richest desktop experience. Rack space and power requirements are also reduced, since no external storage array is needed.