A year has passed since I first published a blog statistics on the number of failures in some models of hard drives
, and now is a good time to its updates.
In the data center Backblaze on December 31, 2014 41,213 worked drives, which are used for our tariff plans with no limit on the amount of disk space. It's more than 27,134 drive the end of 2013. In the past year, most new drives have volume 4 terabytes, and some 6 terabytes.
Statistics of failures for 2014
Let's get right to the point. The table below shows the percentage of failures for 2014. Only the models that we have more than 45 copies. I chose the number 45 because it is the number of disks in the Backblaze Storage Pod
and this is usually sufficient to obtain meaningful values per cent of failures, if they have worked long enough.
The total number of disks in the table 39696. As mentioned, are excluded from the table model, if they are in the presence of less than 45 copies on December 31, 2014. We also removed the boot disks Storage Pod. If you add both of these categories, we have 41,213 employees drive. Some of these discs HGST made under the previous brand Hitachi. We were asked to indicate the brand HGST, and we we respected the request.
What does the failure to Backblaze
The disc is recognized as a failure, if we remove it from the Storage Pod for one or more reasons:
The disc does not start or is not recognized in the operating system. The disk is not synchronized or not synchronized saves in RAID-array. Статистика SMART produces unacceptable values. Sometimes we transfer information from the old disk to the new, recently did when transfer from disk 1, 5 TB drives 4TB. This process is called migration, and such defective disk is not considered a failure, because they are still operable.
What are the best HDD
4 TB drives have proved effective
We liked all the disks to 4TB, which we bought last year. For a reasonable price you get a large amount, and the failures they have really small. The cheapest - Seagate Desktop HDD.15, and we have a lot of drive. More than 12 thousand. The percentage of failures nice small: 2, 6% per year. Low price and reliability are good for business.
Discs HGST, though a bit more expensive, but showed an even smaller percentage of failures: 1, 4%. This significant difference is not enough to strongly influence the buying decision, but when the price drops we buy something how much. These discs have also more than 12 thousand.
What drives with WD 4TB?
We have only one Storage Pod with Western Digital drives for 4TB. How Come? The reason is simple: price. We buy in bulk drives through different companies, and each time you receive a response to our inquiries WD drives were 15-20 dollars doorozhe others. It's too big margin, given that the Seagate and HGST work well.
3TB drives are not very good
HGST Deskstar 5K3000 drives 3 TB have proven high reliability, but they are expensive compared to other models (including similar drives to 4TB of HGST). The percentage of failures Western Digital Red 3 TB of 7, 6% is slightly high, but acceptable. But Seagate Barracuda 7200.14 3 TB - that's another story. We'll talk about them in the following breakdowns blogozapisi.
Confidence in Seagate 4TB
You may ask why the current Seagate drives for 4TB much better than models Seagate 3 TB purchased a couple of years ago. We are surprised. When the wheels 3 TB only appeared in the first year failure rates was 9, 3%. 4 TB drives in the first year show only 2, 6% of failures. I'm pretty sure that the disks to 4TB will work well in the following years.
6 TB and further: it's unclear
We now realize a transition from disk 4 TB 6 TB. So far we have 270 drives Western Digital Red 6 TB, the percentage of failures 3, 1%, but it is only three bad HDD. Statistics show that in the 95% confidence interval real failure rate lies somewhere in the range of 0, 1% to 17, 1%. It is necessary that these wheels have worked longer and collect more statistics before we get reliable figures.
We have a total of 45 drives Seagate 6 TB SATA 3.5, although soon bring a new party. They work for a few months, but none has not failed. Here, too, need to collect more data before you publish reliable statistics.