On Tue, Jul 11, 2017 at 4:32 PM, Carlos E. R. <robin.listas@telefonica.net> wrote:
On 2017-07-11 22:21, James Knott wrote:
On 07/11/2017 04:04 PM, Wols Lists wrote:
For those who don't know, a desktop drive is "within spec" if it returns one soft read error per 10GB read. In other words, read a 6TB drive
s/10GB/10TB/
end-to-end twice, and the manufacturer says "if you get a read error, that's normal". But it will cause an array to fail if you haven't set it up properly ...
What about for those who do know? ;-)
I don't, so please explain ;-)
Carlos, Consider a Raid-5: Then consider no background scrubber is running. Per the specs for most desktop drives, there is reasonable chance (20%) with 2+ TB drives that one or more of the drives will develop undetected bad sectors. Now, assume one of the drives fail. You replace it with a new drive and kick off a re-build. As soon as you hit the bad sector, your rebuild fails and you are stuck working with backups! == Solutions Use Raid-6, but realize in today's era it is still only good for one failed drive at a time. Find drives with significantly higher specs for undetected bad sectors (I don't know if drives like that exist or not). Use a scrubber religiously to make sure there are no undetected bad sectors. == Here's a 8-year old paper arguing even Raid-6 will run out of safety margin by 2019. http://queue.acm.org/detail.cfm?id=1670144 I have no idea if the assumptions it is making are still valid. Greg -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org