Many thanks to all for your posts.  Some thoughts to add (in no particular order):

I have written an additional article based on my experiences designing storage on our array.  It is currently being edited and will be published in the future on this site.

I did not mean to confuse NAS with SAN, but I am not certain that I did either.  I tried to highlight that the newer (since late 2004) CX series from Dell/EMC feature iSCSI which allows users to share ethernet and storage traffic on the same network.  I don't believe that these would be considered NASs.

I do not have a great deal of experience with different SAN vendors.  I did not highlight the brands I currently use in the article because it wasn't a product review and I did not want it to appear as such.  That said, we have installed here a Dell/EMC CX400 (all Fibre), a Dell/EMC CX500 (all Fibre) and an IBM DS4300 (all fibre).  We use McData switches with the Dell equipment and Brocade switches with the IBM.  All told, I think we have around 12 TB of raw storage.  In a previous job, I was privileged to use a Symmetrix SAN (EMC) with their TimeFinder SQL Integration Module (TSIM).  What a pleasure to "snap" an 80 GB full database backup in 3 seconds!

With respect to DAS, I have previous experience with an IBM SCSI (can't remember the model) and current experience (not altogether pleasant) with the Dell PowerVault 220S (1 configured in a cluster, 1 configured as a split bus).  It's not fair for me to compare the performance with our SAN because the DAS is in our test environment and we have made some deliberate compromises in order to save $$$.

As regards performance, I could not be more pleased with the Dell/EMC line.  Two nights ago we loaded a copy of a 279 GB Oracle database from a FireWire External Drive (Maxtor OneTouch II).  The copy process took about 68 minutes (and I had to remove one of the HBA's to fit the PCI FireWire card, so there was no load-balancing during the copy process).  I regularly back up a 200 GB database in about 45 minutes on a different production SQL Server.

Regards,

Hugh Scott