Getting back to the original question, I will say that I, as I expect most of of did, of course considered these back when the first version came out. However, I rejected them based on a few specific criticisms:
1. The power supplies are not redundant. 2. The fans are nut redundant. 3. The drives are inaccessible without shutting down the system and pulling the whole chassis. For my application (I was building a NAS device, not a simple rsync target) I was also unhappy with the choice of motherboard and other I/O components, but that's a YMMV kind of thing and could easily be improved upon within the same chassis. FWIW, for chassis solutions that approach this level of density, but still offer redundant power & cooling as well as hot-swap drive access, Supermicro has a number of designs that are probably worth considering: http://www.supermicro.com/storage/ In the end we built a solution using the 24-drive-in-4U SC848A chassis; we didn't go to the 36-drive boxes because I didn't want to have to compete with the cabling on the back side of the rack to access the drives, and anyway our data center is cooling-constrained and thus we have rack units to spare. We put motherboards in half of them and use the other half in a JBOD configuration. We also used 2TB, 7200 rpm "Enterprise" SAS drives, which actually aren't all that much more expensive. Finally, we used Adaptec SSD-cacheing SAS controllers. All of this is of course more expensive than the parts in the Backblaze design, but that money all goes toward reliability, manageability and performance, and it still is tremendously cheaper than an enterprise SAN-based solution. Not to say that enterprise SANs don't have their place -- we use them for mission-critical production data -- but there are many applications for which their cost simply is not justified. On 21/07/11 12:28 -0400, Ellis H. Wilson III wrote: > > I have doubts about the manageability of such large data without complex > software sitting above the spinning rust to enable scalability of > performance and recovery of drive failures, which are inevitable at this > scale. Well, yes, from a software perspective this is true, and that's of course where most of the rest of this thread headed, which I did find interesting in useful. But if one assumes a appropriate software layers, I think that this remains an interesting hardware design question. > I mean, what is the actual value of this article? They really don't > tell you "how" to build reliable storage at that scale, just a > hand-waving description on how some of the items fit in the box and a > few file-system specifics. THe SATA wiring diagram is probably the most > detailed thing in the post and even that leaves a lot of questions to be > answered. Actually I'm not sure you read the whole blog post. They give extensive wiring diagrams for all of if, including detailed documentation of the custom harness for the power supplies. They also give a a complete parts list -- down to the last screw -- and links to suppliers for unusual or custom parts as well as full CAD drawings of the chassis, in SolidWorks (a free viewer is available). Not quite sure what else you'd be looking for -- at least from a hardware perspective. I do think that this is an interesting exercise in finding exactly how little hardware you can wrap around some hard drives and still have a functional storage system. And as Backblaze seems to have built a going concern on top of the design it does seem to have its applications. However, I think one has to recognize its limitations and be very careful to not try to push it into applications where the lack of redundancy and manageability are going to come up and bite you on the behind. --Bob _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
