my Apple OSX server RAID 14x750TB is running from January 2008 and until now I've changed 4 hard drives. Can anyone suggest how long hard drives can work before failing?
Thank for your opinion, Mario
Well, the life of hard drive depends on the usage. Main factors that decide the hard drive life are:
The last factor on the hard drive that can affect is the file system used and the operating system used and how it is parking the heads when shutting down or when hard drive is in ideal state.
Disk can last from 3 to 7 years on an average but exceptions are there.
Do you mean you have had four HD failures in couple of years in that 14 disk setup? That can be normal, depending on the usage pattern of your hard drives and other conditions.
Hard drives are like humans - some die sooner, some live longer. I have couple of hard drives from the 90's still working (my old beloved Amiga 1200 just won't die... knocks on wood), but on the other hand I've seen some very new HD's failing.
And then there are those sad failure stories from the past, such as IBM's Deskstar, or better known has Deathstar, series, which had some very severe reliability issues around ten years ago.
So, with hard drives, always prepare for the worst and HAVE BACKUPS. Do not trust the drives.
Who knows best how long hard drives will hold? Probably the manufacturers. Look at the warranty offered and use that as a rule of thumb for when the disks are "expected" to stop working. The manufacturers have big money to earn on offering the customers a reasonably long warranty, but not too long.
In small-time use, the statistics of this really doesn't come close to any certain outcomes, but it's the best bet you have. If you're running a big server farm and keep statistics of your disks, you can probably see a very sharp increase in drive failures after the warranty lifetime.
Thus, with common consumer disks, I would say the lifetime to be a bit more than three years. Since the disk prices per storage unit drop significantly during this period, I rotate my disks to never have any disks out of warranty in my main workstation, where a failure would be the most time and work consuming for me.
(Backups is fundamental to data security in all cases, that is not discussable.)
Google released a study in 2007 on their experiences on hard drives: http://labs.google.com/papers/disk_failures.pdf - see figure 2 for drive failures contra lifetime. Read the entire article for more clarity.