What are SAS external storage options (Promise, Infortrend, SuperMircro, ...)?

We just did this here as a test (not my blog):

http://www.natecarlson.com/2010/05/07/review-supermicros-sc847a-4u-chassis-with-36-drive-bays/

It has worked out perfectly. Using off the shelf SuperMicro pieces, we were able to build a 72TB RAW array for about $8,000 total. In hindsight, we didn't need as many SATA controllers, and we never did buy extra disks for caches, as we aren't using the Sun stuff he was talking about.

some of the supermicro backplanes (the vertical card just behind the disk bays) are in fact SAS2 switches. you can daisy-chain several of these backplanes with one or two 4-lane SAS cables and plug a lot of drives on each.

there's even a 4U 45-bay box with just a power supply and some of these on both front and back; no motherboard! Check the manual for details.

Supermicro has a bunch of well-respected SAS enclosures. I don't have personal experience with them, but have a few acquaintences that have had very good luck. They have a 16-slot model that sounds like just what you're looking for.

More than a year ago, backblaze explained how they build a 67TB server for ~8k$.

This is an interesting article, as it shows the different options they chose, as using a custom enclosure rather than buying one.

They gave all the schematics, and you can buy an enclosure here.

At the time the article was written, a petabyte was 81k$ (raw disks). Using their solution, that was only 117k$ (compared to that, dell was 820k$).