I found an old, but interesting, article up on the ExtremeTech website today:

 

    http://www.extremetech.com/computing/170748-how-long-do-hard-drives-actually-live-for

 

While I have seen (and read) the report that Backblaze wrote a couple of years ago, this article summarizes it in a easily readable and understandable form.  When you are reading this article, please remember that this is their experience with thousands of hard drives.  It is impossible to say when which one of the six (or twenty) hard drives in your current system are going to fail.  That type of extraction could only be done if you have couple of hundred systems and then it would be an approximation of the number of drives that might fail in a time period.

Your question is simple to answer. There are two types of hard drives, those that have already failed and those that have not failed yet. All hard drives will fail.

Warranty * 1.1.

As I suspect most of you know, I'm a HUGE fan of backing everything up -- this data simply reinforces the importance of that.

 

Note, however, that most UnRAID systems probably have most of their drives spun down for a significant amount of the time.    This most likely significantly extends the life of the drives ... but doesn't alter the simple fact that all of your data should always be backed up 

Warranty * 1.1.

 

The most important thing to realize about all warranties (and hard disk warranties in particular) is that they are a marketing tool.  The decision process is one of rationalizing the trade-off of increased profits in the current quarter (thru increased sales) vs increased costs in a future quarter (the cost of servicing those warranties). 

 

I have never heard of any company that sets aside money from current sales to meet the future warranty costs of those sales.  They 'pretend' that they are shocked when those costs occur and bemoan the fact of their misfortune!

What I know is this: all electronic devices will fail onetime.

 

If you backup your precious data and give your hard drives a good environment (nice temperature and clean power), you will have little to none headaches with your server. I have 3 1TB WD Green drives with 47300+ hours, thats almost 5 and a half years, and their SMART status are like new.

 

Lessons learned:

 

1) never buy a HDD of the latest model, specially if they are Seagate. Immature/faulty firmware will likely kill your drive;

2) never got more than one drive from a batch; I bought 2x2TB Seagate of the same batch, and they both had failed within 1 week time lapse;

3) take care of your drives, clean and move them with care;

4) ALWAYS BACKUP YOUR DATA.

 

 

Warranty * 1.1.

 

The most important thing to realize about all warranties (and hard disk warranties in particular) is that they are a marketing tool.  The decision process is one of rationalizing the trade-off of increased profits in the current quarter (thru increased sales) vs increases costs in a future quarter (the cost of servicing those warranties). 

 

I have never heard of any company that sets aside money from current sales to meet the future warranty costs of those sales.  They 'pretend' that they are shocked when those costs occur and bemoan the fact of their misfortune!

 

I'm not sure what companies you have had this discussion with, but the companies I have worked for all do exactly that. The cost of manufactured good includes the costs of estimated warranty replacement. There are serious repercussions if the estimate is missed. This is across industries. The auto industry has warranty budgets of about 2% of sales, about $1 billion.

 

Here is the Telsa SEC filing which includes funding warranties http://www.sec.gov/Archives/edgar/data/1318605/000119312514192606/d715897d10q.htm

We provide a warranty on all vehicle, production powertrain components and systems sales, and we accrue warranty reserves at the time a vehicle or production powertrain component or system is delivered to the customer.

Perhaps you are only considering the dealer, not the manufacturer.