January 30, 201511 yr http://www.bhphotovideo.com/bnh/controller/home?O=&sku=1107004&is=REG&Q=&A=details 8760 Power-On Hours Designed for 24 x 7 Operation How can something be designed for 24x7, but only be rated for 8760 hours. That's 1 year before they expect failure? Even if that's the max hours you can have for warranty, the drive advertises 24x7 and 3 year warranty, which is 26280 hours.
January 30, 201511 yr The power-on hours spec is per year ... as you've already noted 24 x 7 operation = 24 hrs/day x 365 days = 8760 hours. The drives are clearly designed to last far longer than that -- with a 3 year warranty and an MTBF of 800,000 hours
February 3, 201511 yr The power-on hours spec is per year ... as you've already noted 24 x 7 operation = 24 hrs/day x 365 days = 8760 hours. The drives are clearly designed to last far longer than that -- with a 3 year warranty and an MTBF of 800,000 hours Unfortunately, the term MTBF is not quite accurate. It should really be expected MTBF. The reason being that the testing is really done as follows: "MTBF sounds simple: the total time measured divided by the total number of failures observed. For example, let's wring out a new generation of 2.5-in. SCSI enterprise hard drives. We run 15,400 initial units for 1,000 hours each (thus our tests take a little less than six weeks), and we find 11 failures. The MTBF is (15,400 x 1,000) hours/11, or 1.4 million hours. (This is not a hypothetical MTBF; it represents current drive technology in 2005.) What does this calculation really mean? An MTBF of 1.4 million hours, determined in six weeks of testing, certainly doesn't say we can expect an individual drive to operate for 159 years before failing. MTBF is a statistical measure, and as such, it can't predict anything for a single unit. We can use that MTBF rating more accurately, however, to calculate that if we have 1,000 such drives operating continuously in a data center, we can expect one to fail every 58 days or so, for a total of perhaps 19 failures in three years." ( Quote from : http://www.computerworld.com/article/2560019/computer-hardware/mtbf.html ) You noticed that I used expected MTBF rather than MTBF. The actual MTBF is the total time that that each of the failed devices ran before they failed. The actual MTBF could include only the hours of those 11 failed drives. (Thus the actual MTBF is less then 1000 hours! No one wants to advertise a number this small so they use the expected MTBF value instead.) For this lot of 15,400 drives, we would have to wait for all of these drives to fail to determine the MTBF. Obviously, no one is going to do that and the manufacturers assume (from past experience) that when they have failures rates as low as this (.071%) after 1000 hours of testing, the failure rates in the field will be low enough that the warranty costs will be manageable. (Warranty duration is more of a marketing/accounting decision then an engineering one!)
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