Backblaze also extends their ingenuity to the server rack. They have designed purpose-built Storage Pod enclosures, and share the schematic freely online. This commendable commitment to information sharing also sheds light on their 'failure rate' data.
The Storage Pod is currently on revision 3.0, with two prior incarnations requiring upgrades to deal with a number of design problems, most notably vibration.
Vibration is every hard drive's enemy, and creates an exponential amount of wear on components. Vibration even has performance implications. A typical desktop HDD experiences a relatively vibration-free existence in a stable environment, and is designed accordingly. One of the major differences in enterprise HDD design is vibration resistance technology. This allows the drive to function well and stand up to the wear and tear of the server chassis and rack.
More HDDs installed in an enclosure raises the amount of vibration. Backblaze packs 45 HDDs per enclosure for maximum storage density. While the drives are initially exposed to vibration from their neighbors inside the server, once placed into the rack, they are exposed to even more vibration from other servers. This creates the 'perfect storm' of vibration, and the use of consumer drives results in horrendous failure rates, as evidenced by the data from Backblaze.
It is no wonder that Backblaze has continued to refine their chassis to provide more resistance to vibration: the early models merely had nylon spacers to dampen vibration. Taking a closer look at their data, we can see that the drives in use the longest suffer the highest failure rates. One likely reason is simple: these older drives are in revision 1.0 of their storage enclosures, which suffer from significant vibration issues that merited a redesign.
Unfortunately for Seagate, these drives are predominantly from their product lines. This paints them in a very unforgiving light due to obvious chassis issues, with a misleading annual failure rate of 25.4% that would surely put Seagate out of business, if it were realistic.
Backblaze has left a significant amount of information out of the disclosed failure rate data. Segmenting these drives to different chassis revisions would be the responsible approach to information dissemination. We can rest assured that the older drives aren't in the best chassis available, revision 3.0 wasn't released until February 2013.