RAID-5 unfortunately is inherently insecure, here is why:
If one drive gets kicked, MD starts recovering to a spare.
At that point any single read error during the regeneration (that's a
scrub) will fail the array.
This is a problem that cannot be overcome in theory.
Yes, I was just getting the same conclusion :-(
Suppose you have 2Tb mainstream disks, with a read error ratio of 1
sector each 1E+14 bits = 1.25E+13 bytes.
It means that you likely get an error every 6.25 times you read the
whole disk!
So in case of failure of a disk, you have 1 possibility over 6 to fail
the array during recostruction.
Simply unacceptable!
I looked at specs of some enterprise disks, and the read error ratio for
them is 1 sector each 1E+15 or each 1E+16. Better but still risky.
Ok.. I'll definitely move to raid-6.
Also raid-1 with less than 3 disks becomes useless the same way :-(
Idem for raid-10 ...wow
Well, these two threads on read errors came out as kinda instructive ...
doh!!
Regards
--
Cordiali saluti.
Yours faithfully.
Giovanni Tessore
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