MTBF and AFR - how long will drive last?

Morlak

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Seagate say that HDD have MTBF of 2M hours. By math, 2M h = cca. 228 years. Does this mean that drive will last 228 years working 0-24h?

Seagate also say that HDD have AFR of 0.44%. So, if I get this right, for first year is 0.44%, for second 0.88% and so on. By this "half-life" of HDD when half of them will be dead is - 114 years of constant work 24h. My math this is in correlation with upper result, 114 is half of 228.

To me, 228 years or 114 half-years sound too good to be true.

So, my questions are:

1. Am I wrong in my math?
2. If I am, how can I calculate approximately how long will drive last using known MTBF and AFR from manufacturer?

Thank you. ;)
 
Thanks!

So, the real formula is R(T) = exp(-T/MTBF). Nice to know, I'm calculating all odds right now. :)


Just to add, by this formula there is 64% chance that my disk will survive 100 years, and 80% chance that it will survive 50 years. Quite long, perhaps that is the reason why it cost so much.
 
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That is assuming the MTBF figure released by the manufacturer is to be believed. Not that many hard drive models out there can claim to have survived for 50+ years, so the MTBF figures are, right now, mostly just based on early defect counts and a lot of longevity speculation.
 
Note that a major assumption of the MTBF methodology is that the product has a CONSTANT failure rate.

If you buy that the actual failure rates for hard drives are the same in the first year as in the fifth year, then I have a bridge in Brooklyn that you might also like to buy.
 
2. If I am, how can I calculate approximately how long will drive last using known MTBF and AFR from manufacturer?

Here's the full Seagate disclaimer on MTBF & AFR from the Enterprise series drive manual:

Seagate Constellation ES.3 SATA Manual said:
The production disk drive shall achieve an annualized failure-rate of 0.44% (MTBF of 2,000,000 hours) over a 5 year service life when used in Enterprise Storage field conditions as limited by the following:
•8760 power-on-hours per year.
•HDA temperature as reported by the drive <= 40°C
•Ambient wet bulb temp <= 26°C
•Typical workload
•The AFR (MTBF) is a population statistic not relevant to individual units
•ANSI/ISA S71.04-2013 G2 classification levels and dust contamination to ISO 14644-1 Class 8 standards (as measured at the device)

Note the operating conditions specified. Most importantly, see the bolded/underlined bullet -- the MTBF and AFR do not apply to individual units. You shouldn't rely on them to predict your drive reliability unless you're running at least 10,000 units within the specific conditions. In the first year then, you should budget for 44 of those drives failing.
 
then I have a bridge in Brooklyn that you might also like to buy.

What is wrong with the bridges in Brooklyn? :D

Note the operating conditions specified. Most importantly, see the bolded/underlined bullet -- the MTBF and AFR do not apply to individual units. You shouldn't rely on them to predict your drive reliability unless you're running at least 10,000 units within the specific conditions. In the first year then, you should budget for 44 of those drives failing.

I see now. I wish my calculations were true. :(


Thank you guys for clearing this matter. ;)
 
I see now. I wish my calculations were true. :(

For reliability purposes, consider other "guaranteed" specs such as the unrecoverable error rate (1 in 10^15 for enterprise, 1 in 10^14 for consumer) and the warranty length (usually 5 years for enterprise, 1-2 for consumer). In general, enterprise drives will have a lower failure rate than consumer drives. If you can afford it, go for the enterprise drives. If you're going for consumer drives, the consensus is that the HGST Desktop NAS series are the best around.
 
The production disk drive shall achieve an annualized failure-rate of 0.44% (MTBF of 2,000,000 hours)
...
You shouldn't rely on them to predict your drive reliability unless you're running at least 10,000 units within the specific conditions.
Of course, all studies with statistically significant disk populations point to AFR an order of magnitude higher than what is stated by the manufacturer, except maybe HGST.

In general, enterprise drives will have a lower failure rate than consumer drives.
This has been shown to be untrue by backblaze. The advantage of enterprise disks is longer warranty, TLER and constructive measures to reduce vibration in large disk arrays (which impacts seek performance), not lower failure rates.
 
I bought 3 HGST 4TB drives and so far 2 of them have gone out. I bought 3 2TB seagates and only 1 of them lasted also. I ran both set of drives in a raid and they were used to record tv shows with WMC. At this point I don't know what brand of drives I can try next. The only drives I never had to replace are some old 2TB Samsung drives that were produced before the flood in Thailand. I regret not buying more than 4.
 
I bought 3 HGST 4TB drives and so far 2 of them have gone out. I bought 3 2TB seagates and only 1 of them lasted also.

With an extremely small sample size like this you could just have really bad luck . Remember that someone has to have the ~1% of drives that fail annually for HGST and the 4% or so of drives that fail annually for Seagate. However I would check the voltages on your power supply. It's definitely possible that your environment is destroying the drives.
 
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I bought 3 HGST 4TB drives and so far 2 of them have gone out. I bought 3 2TB seagates and only 1 of them lasted also. I ran both set of drives in a raid and they were used to record tv shows with WMC. At this point I don't know what brand of drives I can try next. The only drives I never had to replace are some old 2TB Samsung drives that were produced before the flood in Thailand. I regret not buying more than 4.
Do you have a vibration issue? Perhaps a power supply issue?
 
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How exactly have your drives failed? What are the exact symptoms or indications you are using to determine that they have failed? Have you done any follow-up tests to determine failure modes? Have you examined the SMART attributes?
 
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MTBF is all BS. I had two of three identical Seagate NAS drives purchased at the same time fail within 4 months of each other. The first 8 months before warranty expires, the second 4 months later. I am waiting for the last one to fail so I can have it replaced too.
 
I had two of three identical Seagate NAS drives purchased at the same time fail within 4 months of each other.

With a small sample size you could have 0 failures or all of your drives could fail yet all of the drives of the same exact model in existence may experience a 4% annual failure rate.
 
Do you have a vibration issue? Perhaps a power supply issue?
I don't have any vibration issues. I don't think I have a power supply issue. The power supply never unexpectedly shutdown or reboot unless there is a power outage. I have a 380W earthwatts running 3 HGST 4tb, 3 Seagates 320 GB drives, 120gb Kingston ssd, H700, a i5 cpu, and a EVGA GT 610 graphics card. The graphics card is ok in a power supply 300 and greater. The 3 older seagates hard drives in a software raid are still working.

Or heat? Like prolonged 55+?
The only time the cpu temperature get close to 54 is when I run hand brake. I convert the videos on my old seagates drives and not the hgst when I run hand brake. During this time of the year when I run handbrake my temperature stay below 50.

How exactly have your drives failed? What are the exact symptoms or indications you are using to determine that they have failed? Have you done any follow-up tests to determine failure modes? Have you examined the SMART attributes?
I run these drives on a raid 5 array using a perc H700. After a while 2 drives eventually failed in my array. When the first drive failed I put it in another pc and tried to format it. The drive would not format and error out. I also ran the WinDFT tool and don't remember exactly what it said. Currently I am trying to format the 2nd drive that failed. When it get done I will run the SMART tool and let you know what it says.

I mostly record tv shows to this array with Windows Media Center and HDHomerun. Do anyone think the constantly reading and writing to this array can cause problems with these drives?
 
The power supply never unexpectedly shutdown or reboot unless there is a power outage. I have a 380W earthwatts running 3 HGST 4tb, 3 Seagates 320 GB drives, 120gb Kingston ssd, H700, a i5 cpu, and a EVGA GT 610 graphics card.

I would look at the voltages with a digital volt meter.
 
The only time the cpu temperature get close to 54 is when I run hand brake. I convert the videos on my old seagates drives and not the hgst when I run hand brake. During this time of the year when I run handbrake my temperature stay below 50.
Not the CPU temperature, the HDD temperatures.
 
I don't know which revision of the Earthwatts you have. I had not-so-good experiences with the first Earthwatts EA430 a long time ago.

Do you overclock your I5?

With so many sudden drive failures, I'd suspect excessive heat and/or an unstable power supply. The power supply is among the cheapest to switch out and can be reused in a new build, so I recommend -- assuming no overlooking -- you get at least a 430W Corsair PSU (regular on Newegg for $20 AR) and replace the 380W Earthwatts.
 
:confused: How are you doing that? Are you giving us power on hours or you're continuously recording & playing back / editing from the drives for the number of hours you've listed?
I am giving you hours. I just look at how often I record. Those numbers are not continuously. I record between 7.5 hours to 15 hours a day. I record about 6 hours Monday-Friday on just ESPN alone.

Also can you tell me how can I measure the temperature of a hard drive behind a array? I have a perc H700.
 
I don't know which revision of the Earthwatts you have. I had not-so-good experiences with the first Earthwatts EA430 a long time ago.

Do you overclock your I5?

With so many sudden drive failures, I'd suspect excessive heat and/or an unstable power supply. The power supply is among the cheapest to switch out and can be reused in a new build, so I recommend -- assuming no overlooking -- you get at least a 430W Corsair PSU (regular on Newegg for $20 AR) and replace the 380W Earthwatts.

I do not overclock.
 
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