Previously I've talked about how using local storage can help reduce the costs of desktop virtualization.  Paul Wilson tested this type of environment to determine that it is indeed possible.  So we have a new design decision, which way will you go?

Before making the decision, you have to determine if local storage is good enough for your environment or if you need shared storage.

Local Storage
Local storage is the storage located within the server running a hypervisor (XenServer, Hyper-V, vSphere).  By using the local drives, the following are important considerations to remember:

1. Live Migration: being able to move a running VM from server-to-server is not available.  Because other servers cannot see and access local storage, live migration is not an option, however, many organizations have decided not to use this functionality for virtual desktops.
2. Server Balancing: Server balancing allows the pool of hypervisor servers to be rebalanced so their loads remain similar throughout the day.  In order to do active server balancing, live migration functionality is required.  However, if server loads are balanced on virtual machine startup, the balancing is still an option.
3. Server Costs: In order to use local storage, the server must have additional, fast hard drives and fast array controllers. This increases the cost for each server, although these costs are usually lower than an enterprise shared storage solution.

Shared Storage
Shared storage is located on a centralized storage system (SAN or NAS type devices). By using shared drives, the following are important considerations to remember:

1. SAN Costs: Shared storage solutions are expensive infrastructure components.
2. Server Costs: Connecting a server to a shared storage infrastructure requires some type of hardware connection, either network cards, fibre-channel cards, or some other connection method. This has an impact on the server, but also on the underlying infrastructure to support the increased traffic (network switches)
3. Expertise: In order to utilize an enterprise storage solution, the organization must have expertise.  If a team is not already ingrained within the organization, this must be done in order to support this important infrastructure component and your larger desktop virtualization goals.

So which option is right for you? You tell me.  If you don't need live migration, and don't already have a enterprise storage solution, you might be better off by going with the local storage option.  However, if you have capacity, technical expertise, and experience with enterprise storage then use what you got and go down the shared storage path.

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