Four TB good ,three TB bad, says disk drive reliability study

Some hard drives are more equal than others


We're not entirely comfortable with cloud backup outfit Backblaze's data on disk drive reliability, but the company has just popped out another year's worth of analysis on which drives hang around longest. With due scepticism, let's have a look.

For the uninitiated, Backblaze does cloud storage and backup using home-brew arrays called Storage Pods that it has open-sourced. Storage Pods can work with just about any kind of disk, be it intended for enterprise or consumer desktop use. The company regularly reveals selective bits of analysis about its rig, offering insights on disk drive longevity among other matters.

This week, the company offered up an analysis of the performance of its diverse disk drive fleet, which comprises 39,696 drives holding customer data (minus a few models represented by fewer than 45 drives). The data reports failure rates, with failures defined as either drive death, inability to work in a RAID array or failure to meet unspecified performance criteria.

Here's Backblaze's table of that data.

Backblaze Hard Drive Failure Rates Through December 31, 2014
Name/Model     Size     Number
of Drives
Average Age
in years
Annual
Failure Rate
95% Confidence
Interval
HGST Deskstar 7K2000
(HDS722020ALA330)
2.0 TB 4,641 3.9 1.1% 0.8% – 1.4%
HGST Deskstar 5K3000
(HDS5C3030ALA630)
3.0 TB 4,595 2.6 0.6% 0.4% – 0.9%
HGST Deskstar 7K3000
(HDS723030ALA640)
3.0 TB 1,016 3.1 2.3% 1.4% – 3.4%
HGST Deskstar 5K4000
(HDS5C4040ALE630)
4.0 TB 2,598 1.8 0.9% 0.6% – 1.4%
HGST Megascale 4000
(HGST HMS5C4040ALE640)
4.0 TB 6,949 0.4 1.4% 1.0% – 2.0%
HGST Megascale 4000.B
(HGST HMS5C4040BLE640)
4.0 TB 3,103 0.7 0.5% 0.2% – 1.0%
Seagate Barracuda 7200.11
(ST31500341AS)
1.5 TB 306 4.7 23.5% 18.9% – 28.9%
Seagate Barracuda LP
(ST31500541AS)
1.5 TB 1,505 4.9 9.5% 8.1% – 11.1%
Seagate Barracuda 7200.14
(ST3000DM001)
3.0 TB 1,163 2.2 43.1% 40.8% – 45.4%
Seagate Barracuda XT
(ST33000651AS)
3.0 TB 279 2.9 4.8% 2.6% – 8.0%
Seagate Barracuda XT
(ST4000DX000)
4.0 TB 177 1.7 1.1% 0.1% – 4.1%
Seagate Desktop HDD.15
(ST4000DM000)
4.0 TB 12,098 0.9 2.6% 2.3% – 2.9%
Seagate 6 TB SATA 3.5
(ST6000DX000)
6.0 TB 45 0.4 0.0% 0.0% – 21.1%
Toshiba DT01ACA Series
(TOSHIBA DT01ACA300)
3.0 TB 47 1.7 3.7% 0.4% – 13.3%
Western Digital Red 3 TB
(WDC WD30EFRX)
3.0 TB 859 0.9 6.9% 5.0% – 9.3%
Western Digital 4 TB
(WDC WD40EFRX)
4.0 TB 45 0.8 0.0% 0.0% – 10.0%
Western Digital Red 6 TB
(WDC WD60EFRX)
6.0 TB 270 0.1 3.1% 0.1% – 17.1%

The company's impressed by the four-terabyte drives it's bought lately, praising their reliability, bang-for-byte-and-buck and falling failure rates compared to drives it acquired in 2013. It's also very pleased with older 1.5TB Seagate desktop drives, which are hanging in there with impressively low failure rates.

3TB drives continue to disappoint, although as our previous analysis shows Seagate's acknowledged a problem in 2013-release drives.

HGST drives do better at Backblaze than those from Western Digital or Seagate, proving more reliable by a couple of per cent.

Backblaze's workloads aren't typical, it doesn't certify drives and it's not running an enormous fleet of drives by the standards of today's cloud operators. It is, however, the only entity currently releasing this kind of data. Google's done so in the past and Microsoft has of late been candid about some aspects of Azure's operations. Feel free to fling us some disk data, folks: Backblaze's results are interesting, but we'd like meatier numbers to work with. ®

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