Hello,
As far as I understand, md-raid relies on the underlying devices to
inform it of IO errors before it'll seek redundant/parity data to
fulfill the read request. I have, however, seen certain hard drives
report successful reads while returning garbage data.
Is it possible to set md-raid into a paranoid mode, in which it reads
all available data and confirms integrity? Here's how it would work:
RAID6: read data + parity 1 + parity 2. If 1 of the 3 mismatches,
correct it, and write corrected data to the corrupt source. Log the
event. If all 3 disagree, alert user somehow.
RAID5: read data + parity. If they mismatch, alert user somehow.
RAID1: read data 1 + data 2. If they mismatch, alert user somehow.
You can see this is mostly useful for RAID6 mode, where there is a
chance at automated recovery. However, it can also be used to prevent
silent data corruption in the other modes, by making it not silent.
--Bart
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