Cloud backup provider Backblaze has published its findings for the tens of thousands of disks that it operated and says that the standout reliability leader was HGST. Backblaze had 41,213 disk drives spinning in its data center. Most of the new drives are 4 TB drives, and a few are the new 6 TB drives.

According to the tests, Western Digital's HGST models showed low failure rates; at worse, 2.3 percent failing a year. This includes some of the oldest disks among Backblaze's collection; 2TB Desktop 7K2000 models are on average 3.9 years old, but still have a failure rate of just 1.1 percent.

Seagate's 1.5TB models (Barracuda 7200.11 and Barracuda LP) gave failure rates of 23.8 and 9.6 percent, even though they were the oldest disks in the test (average ages of 4.7 and 4.9 years, respectively). However, their poor performance was eclipsed by the 3TB Barracuda 7200.14 units, which had a whopping 43.1 percent failure rate, in spite of an average age of just 2.2 years.

Newer Seagate disks also show more encouraging results. The 4TB HDD.15 models show a low 2.6 percent failure rate. Coupled with their low price-Backblaze says that they tend to undercut HGST's disks.

A drive was recorded as failed in case it stopped spinning or connecting to the OS; if it would not sync, or stay synced, in a RAID Array. But have in mind that Backblaze operates disks outside of the manufacturer's specified parameters - 24/7 operation, vibration.

The HGST Deskstar 5K3000 3 TB drives have proven to be very reliable, but expensive relative to other models (including similar 4 TB drives by HGST). The Western Digital Red 3 TB drives annual failure rate of 7.6% is a bit high but acceptable.

Backblaze is also beginning the transition from using 4 TB to using 6 TB drives. Currently the company has 270 of the Western Digital Red 6 TB drives. The failure rate is 3.1%, but there have been only 3 failures. The statistics give a 95% confidence that the failure rate is somewhere between 0.1% and 17.1%.

The company is also having 45 of the Seagate 6 TB SATA 3.5 drives, although more are on order. They’ve only been running a few months, and none have failed so far, Backblaze says.