In late 2013, cloud service provider Backblaze released information about hard drive failure rates used in their facilities collected over a three-year period. The study was one of the first real-world, comprehensive examinations on server-level claims of hard drive reliability, and drew a great deal of attention. An update with new information from between the end of the last study and December 31, 2014 was posted today.
The study includes a table with 17 different models of hardrives, of which Backblaze has at least 45 each of, which is the number of drives needed to fill one of their Backblaze Storage Pods. Whether or not a drive "failed" was based on a number of factors, but older drives that were removed in favor of newer 4TB drives and kept in reserve as backups didn't fall into the category.
Seagate's ST4000 line of 4TB drives was ranked surprisingly highly in the area of the reliability-to-price ratio. The study doesn't discuss what the drives cost exactly, only mentioning they cost less than most. The average annual failure rate for those models was 2.6 percent per year, with the online backup company investing in 12,100 of the units. Both last year and this year, lower-end consumer Seagate drives were not as well regarded, garnering some of the highest annual failure rates in the survey.
An ST3000 3TB 7200rpm drive, for example, had a staggering 43.1 percent annual failure average across just over 1,000 drives. Seagate's consumer-level drive lineup did not do well in last year's survey either, which generally found that the median lifespan of a typical hard drive (running 24-7) was six years, with the chances of failure increasing substantially after the fourth year on average.
Last year, HGST (formerly known as Hitachi) did very well, with a survival rate of 96.9 percent of the drives continuing to spin in Backblaze's storage pods after 36 months. This year's study shows the existing HGST drives still spinning, with the lowest failure rate for their age, though the study noted that the price ratio was a bit high. The same went for the new 4TB drives from HGST; though higher in price, the failure rate was the lowest for that category when average age of the drives is factored in.
The study goes on to suggest that while HGST still has the lowest failure rate, the 0.8 percent difference in failure with Seagate's 4TB drives isn't enough to overcome Seagate's generally lower prices. However, if buyers can get the HGST on sale, it is the more highly recommended for reliability.
The study doesn't go into great detail about drives claimed to be optimized for data center loads -- the vast majority of drives used were consumer-level products. The Backblaze drive racks hold up to 48 drives per array, and it is possible that vibration and heat may have caused some premature failures of drives, but the general results of the study remain valid, if perhaps time-compressed somewhat.
