Clearly from the data collected by the storage company the life expectancy of the hard disk

ByKevin Collins

There are many people whose computers and computers are getting deeper into work and private, and many data and information are saved on the hard disk of the PC. However, if trouble happens to such a hard disk, and the data inside is lost ... .... As long as it is a machine, it is definitely a hard disk that fails someday, but interesting data on annual life of such a hard disk is announced.

Back Blaze Blog »How long do disk drives last?

I announced this data to develop online backup and data backup software in the USABackblazeIt is a company. We analyzed the data acquired from the service over the past five years and predicted the life of the hard disk. Of the tens of thousands of hard disks operating at the company, 78% of the hard disks do not have problems and only 22% of the hard disks are known to suffer from some trouble in the past 4 years.

◆ Hard disk usage environment
Backblaze can mount 48 hard disksBackblaze Storage PodWe installed a dedicated dock called a data center rack and used it. Every time new users are added, hard disks are being expanded, and the current storage capacity has reached 75 petabytes.

◆ Hard disk used
What is used in this system is not designed exclusively for servers, it is a hard disk for consumers that is generally on the market. As manufacturers say "It is not designed for workloads that run full at 24 hours / 7 days a week in a RAID environment", the company introduces redundancy software to protect data .

Nearly all of the hard disks used are of the type that is exposed and exposed like a "bulk article" or "built-in type". When the "hard disk crisis" triggered by major flood damage occurred in Thailand in 2011 occurred, it became very difficult to get such bulk goods cheaply. In order to cope with that, Backblaze purchased an external hard disk of the USB connection in town, disassembled, and used it as an alternative hard disk. The hard disk that was introduced at that time reaches as much as 6 petabytes, which is included in this data as well.

The table below shows the hard disks used in the data center by manufacturing year. As the company's growth and users increase, you can see that the number of hard disks continues to increase.

◆ Breakdown rate and "bathtub curve"
First of all, what does "failure rate" mean? It is as follows. A hard disk of one manufacturer guarantees 100% stability for six months, but fails immediately after that. In order to keep 100 hard disks running at all times, it is necessary to replace all drives twice a year. Since it is necessary to replace 200 hard disks in one year, the annual failure rate in this case is 200%.

When predicting the failure occurrence time of the equipment, "Bathtub curveWhat is called what is called out. At the time of equipment failure, it is caused by a factory default failureInitial failure period,Accidental failure period, Due to consumption of equipmentWear failure periodThere are three types of theory.

The graph of this theory is consistent with the actual number of failure occurrence data of Backblaze. The following graph shows the number of failure occurrences per quarter, the failure rate which had been around 5% for the first 18 months shows a decline afterwards, but markedly increases at the timing when it reaches 3 years It shows the trend of. It seems that this "third year" can be thought of as one point of hard disk life.

◆ Calculate life expectancy
What is the term "life expectancy of hard disk"? For life expectancy of human beings, the life expectancy is assumed to be the average life expectancy minus age. The life expectancy of a baby just born in 2010 is 67.2 years old, and even if you live to 120 years old, the average life expectancy is 67.2 years old. As far as one hard disk is concerned, almost all hard disks will have a lifetime within 10 years. However, there are things that will continue to move from 20 to 30 years, and there is a possibility that some things will have an adverse effect on the average calculation. Therefore, such outliers are to be eliminated in the calculation stage.

This figure will reveal the results soon. The center value of the life expectancy of a new hard disk is clarified, and it turns out "at which point, half of the hard disks will have a lifetime".

◆ Hard disk survival rate
Even with the Internet, it is very difficult to get the answer of "hard disk life". What you can get is a general story,GoogleYaCarnegie Mellon University(CMU) statistics, etc., there are no clear answers.

The graph below shows the survival rate of the hard disk used by Backblaze. For the first 18 months, we can see that the failure rate has changed at an annualized rate of 5.1%, and from 19 months to 36 months at a low level of 1.4% per annum. And since around 36 months, the failure rate is rapidly increasing to 11.8% (the gradient of the graph is not flat but suddenly comes along the angle).

The graph below shows how much hard disk survived as a whole. Even at the end of 4 years, it is clear that 80% of hard disks do not have any problems.

◆ How long can you use the hard disk afterwards?
What will happen to the life of the hard disk after five years? Regarding this, both Google and CMU have not issued data on hard disks over 5 years, but CMU has commented on the conclusion of the paper that "failure rate will increase over 5 years" It is worth noting. All of the hard disks used by the company are from brand-new products, and we have not yet acquired data on hard disks over five years, and we will continue to continue data in the future.

Based on the chart above, if you predict the point where half of the hard disks will have reached their end of life, the intermediate point of the life of the hard disk will be around a little over six years.

In this way it turned out that the life expectancy of hard disks may be longer than expected in general. Nonetheless, it is also a clear fact that it will be broken someday, so it is important to take risk avoidance measures such as backup and RAID construction in case of emergency situation.

in Hardware, Posted by darkhorse_log