In an interesting observation from storage leader EMC, who also happens to own the VMWare franchise, it seems that NAS is overtaking SAN as the storage platform of choice for virtual server environments. This seems especially true for VI3 automated environments, where namespace and connectivity issues make NAS much simpler to configure and access in a highly dynamic environment than SAN.
(As an aside, I also love the quote in the article where EMC Corp. vice president of technology alliances Chuck Hollis pointed out that "To be honest, we're not seeing a whole lot of high performance stuff being put on VMware." Don't be fooled, most large datacenters will always have applications that can not be virtualized without a penalty.)
I would have to say that EMC's observation aligns with my own, as it has been clear for some time that NAS has offered some advantages over SAN for application storage in Cassatt environments. It boils down to accessibility--SAN requires special interface cards, and very few (if any) of the SAN switches today are remotely configurable by an automation environment. There are cool vendors out there (see 3PAR and DataCore, for example) that have tools to increase the dynamic nature of SANs, but NAS tends to rule here.
The article also notes some reasons why performance is overrated in the SAN vs. NAS comparison. Low end (e.g. workgroup class) NASs may suffer from some limitations based on network bandwidth, but TOE NICs and multi-NIC high-end NAS configurations are "widening the highway", allowing NAS performance to catch up to, and even surpass SAN. Cost/performance numbers are still something to consider, but I expect that the only apps that will be using fiber SAN in five years will be extremely high I/O applications, such as OLTP apps.
Let me give you quick reason why all of this is important: multitenancy. The Software as a Service (SaaS) and Managed Hosting Provider spaces have embraced the concept of one infrastructure supporting a large number of unique, individual clients. However, to achieve this, one needs to be able to "virtually" isolate each client from each other for both security and data integrity reasons.
To achieve this isolation, it is necessary to uniquely assign each customer two things: network access and (you guessed it) storage. Managed hosting providers and SaaS vendors are looking for tools that will allow them to dynamically assign a server (and thus, its hosted software) to specific VLANs and LUNs/namespaces. This will be a key focus for automation vendors in the next 2 years or so.
What do you think? How do you plan to address storage in your automated data center?