Battling for affordable transport

SANs for small to midsized businesses open up new cost-containing drive technologies, but it's hard to kick the FC transport habit

I have been working mostly in my lab lately, resisting temptations to visit more shows or vendor sites. It's not that I don't like traveling (on the contrary, I enjoy it) but a few SAN arrays waiting for review had piled up in my lab and were making me feel guilty every time I walked by.

The term "SAN arrays" often evokes images of towering, refrigerator-size units, but the ones currently co-habiting in my lab are instead self-contained 1U and 2U modules -- entry steps to storage networks for the now-popular SMB (small to midsize business) customers.

A casual observer could easily confuse these units with application servers, but their weight is a giveaway. My FedEx driver was definitely not confused: "You must have some very big computers in there," she commented while we unloaded the box containing the NexStor 4700F.

The 4700F is a SAN array by nStor, a company that has been in the storage business for quite some time and also offers lines of larger storage arrays for midrange customers.

The 4700F's shipping weight of almost 80 pounds more than justifies my FedEx driver's comment. In fact, this 2U array came to me with 12 WD740 SATA (Serial ATA) drives from Western Digital, which -- when added to the controllers, fans, and other circuitry -- makes for considerable heft.

I should probably mention that the WD740 drives balance a rather small capacity of 74GB per drive with astonishing performance and reliability, previously attainable only with Fibre Channel or SCSI.

The 4700F offers an interesting combination of pragmatism and innovation that brings together the canonical FC (Fibre Channel) transport with relatively new SATA controllers and drives. This combination should play well with cost-conscious customers, because even if it uses the most expensive drives, a SATA-based array costs considerably less than a comparable SCSI or FC unit.

Once I finished sliding all the WD740s into their slots (to protect my back and nStor's units, packaged separately), my total capacity was less than 1TB. However, by trading speed for capacity, it is possible to mount slower SATA drives with 250GB capacity on the 4700F, which gives you a comfy 3TB per array. By mounting other arrays, one can grow the unit by similarly sized expansion steps up to 60TB in a single, full-height rack.

Although I have an FC switch and HBAs in my lab, nStor felt it proper to send over a couple of recent FC adapters from QLogic to mount in my servers. While preparing the test bed, I couldn't help thinking about how vendors differ in their perception of SMB customers’ requirements.

For instance, nStor has made no concessions (at least not yet) to a cheaper alternative to FC transport, such as iSCSI (Internet SCSI).  And the company is not alone: The difference in performance of 2Gbps versus 1Gbps for iSCSI seems to be a big deterrent for many vendors.

"You would not ask me this question a year from now" is the answer I got from the brass of a large storage vendor, which shall remain nameless. The question, of course, was why his company was not offering iSCSI connectivity at the low end; the explanation for his answer built on the assumption that iSCSI's speed would leapfrog FC.

Well, I can wait until next year with no problem, but can SMB customers wait that long? Or will they simply adjust to the slower pace of the less-expensive iSCSI? One thing I'm sure of: with entry-level FC equipment becoming more affordable, iSCSI is losing some of its luster. 

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