question about fsck failing during startup

[scar]

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hi, during a routine check of disks during startup, fsck failed due to
read failures.  it said to run it manually, so i did.  again came the
read errors.  i just ignored them all.  i think there were 32 in all and
then fsck finished and the system booted up fine after that.  i decided
to then reboot into recovery mode and drop to a root shell, unmount the
root filesystem, and run 'e2fsck -c' in order to update the bad blocks
list.  i think it found the same 32 sectors and updated the bad blocks
file.  the system has been running stable since.

so, my question is: is everything ok?  i realize the hard drive should
probably be replaced soon, but as long as i have marked the bad blocks
it should be ok for now?  (btw, it is a 1.8" PATA IDE drive, impossible
to find, probably $100's to replace, so it probably won't get replaced
soon).

i guess my question arises out of a misunderstanding of what the routine
check during startup is actually doing.  does it check the whole surface
of the drive that the filesystem is allocated to?  or does it just check
the used area?  if it just checks the used area, then that means those
read failures occurred in places that had data.  if that is the case,
then how can i find out what data is no longer accessible?  it must not
be too important as everything has been stable and i don't notice
anything missing.
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