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Sander wrote:
Michael Tokarev wrote (ao):
Most problematic case so far, which I described numerous times (like,
"why linux raid isn't Raid really, why it can be worse than plain
disk") is when, after single sector read failure, md kicks the whole
disk off the array, and when you start resync (after replacing the
"bad" drive or just remapping that bad sector or even doing nothing,
as it will be remapped in almost all cases during write, on real
drives anyway),
This particular case has been addressed in the latest kernels. md will now attempt to write the bad
block back using reconstructed data and the disk will only be punted after multiple failures or a
write failure (if my understanding of the patches is any good anyway)
If the (harddisk internal) remap succeeded, the OS doesn't see the bad
sector at all I believe.
If the disk can get a good read then it will re-map on the fly and the OS has no idea there was an
issue. If not then it returns a read error to the OS. When that sector is next written it will be
re-mapped by the drive and the error disappears.
If you (the OS) do see a bad sector, the disk couldn't remap, and goes
downhill from there, right?
With the older md code, yes, however as stated above this should almost become
a non-issue now. (yay!)
Brad
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