On Mar 10, 2017, at 9:28 AM, Valeri Galtsev <galtsev@xxxxxxxxxxxxxxxxx> wrote:
>
>
> On Fri, March 10, 2017 9:52 am, Warren Young wrote:
>> On Mar 10, 2017, at 6:32 AM, James B. Byrne <byrnejb@xxxxxxxxxxxxx> wrote:
>>>
>>> On Thu, March 9, 2017 09:46, John Hodrien wrote:
>>>>
>>>> fsck's not good at finding disk errors, it finds filesystem errors.
>>>
>>> If not fsck then what?
>>
>> badblocks(8).
>
> And I definitely will unmount relevant filesystem(s) before using
> badblocks…
You don’t necessarily have to. The default mode of badblocks is a non-invasive read-only test which is safe to run on a mounted filesystem.
That said, a read-only badblocks pass can give a false “no errors” report in cases where a non-destructive read-then-write pass (-n) will show errors.
Alternatively, a read-only pass may show an error that a read-then-write pass will silently bury by forcing the drive to relocate the bad sector.
In extreme cases, you could potentially fix a problem with a read-random-random-write pass (-n -t random -t random) because that will statistically flip all the bits at least twice, which may rub the drive’s nose in a bad sector, forcing a reallocation where a normal read-then-write pass (-n alone) may not.
Hard drives are weird. It is only through the grace of ECC and such that they approximate deterministic behavior as well as they do.
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