Our Experience with Backplanes
The original Backblaze Storage Pods were designed around port multiplier backplanes. These are circuit boards that have multiple SATA hard drive connectors (5, in this case), and one SATA cable connector. This allows up to 5 hard drives to be plugged into the board, and multiplexed and sent through 1 cable to a shared SATA port. Therefore, 45 drives require only 9 cables and SATA ports. This is economical as well as practical. Combined with Backblaze's vertical mounting, this was a brilliant design.
There are a few restrictions and caveats, of course. The SATA adaptors must be chipset compatible with the backplane port multipliers, and drivers are required. Physical dimensions of 5 port boards follow a defacto standard. Also, data for 5 drives shares 1 SATA cable (3Gbit in the original design), limiting performance to 60 MBytes per second per drive (whereas mechanical drives can transfer approximately 150 MBytes per second). But all things considered, limited throughput speed was a reasonable sacrifice for Backblaze, and backplanes were what drove the success of Pods 1.0 to 3.0.
Backblaze has operated their business successfully for years now, mostly with backplane machines. But we experienced a number of challenges when we sold these to the larger storage community.
Conflicts with the Needs of Other Users
At 45 Drives, it is in our nature to get to know our customers and what they are doing (or want to do) with their pod. And we really can't help thinking about variations to the design, and how it might improve the pod for various applications. Because we are part of Protocase, a mass customizer and the fastest low-volume metal manufacturer on earth, evolving the design was an inevitable step for us and continues to be an ongoing endeavour. It's what we do.
Over the years, we have listened to feedback from hundreds of very bright people involved in a wide variety of applications. In addition to the standard pod designs, we have built a large number of customized pods (in fact, we end up customizing almost 50 per cent of pods to some degree).
Here's a summary of feedback we've received about the original pod design: