Q: How do you determine if NAS, FC SAN or iSCSI SAN the right fit for a customer?
I realize that this question can often be similar to a religious discussion, but there is some basic data that you can use to help determine the best solution. Generally speaking, NAS was designed for sharing files in the open systems environment. If the customer is sharing files among a number of clients, or servers, NAS will be an extremely efficient way to service your customer's needs. Make sure that if there is a specific application being used that it is compatible with not only NAS, but the specific NAS platform you wish to specify. The FC vs. iSCSI debate is a little bit more difficult. They both provide virtual disks to a host using encapsulated SCSI over a lower-level transport such as Fibre Channel or IP. It looks like local disk to the application, so there really shouldn't be much to worry about in the way of application compatibility (still, you should check with your application vendor to ensure there aren't any gotchas for a specific SAN or iSCSI array with their app). It really comes down to price and performance. Don't be fooled by the typical claim that Fibre Channel is faster than iSCSI. At low speeds and on small arrays, the performance and latency of iSCSI will be comparable to FC. It's important that you understand your customer's performance requirements and validate with the vendor that it can meet those requirements over the chosen transport. You will find that iSCSI will meet many customer requirements and save them a ton of cost in infrastructure such as HBAs and switches.
This was first published in January 2008