At 2:14 PM +0930 7/5/07, Tim wrote: >Tim: >>> As far as I can tell, you can get SMART to check drives, but it offers >>> nothing to fix them up. > >Tony Nelson: >> SMART's automatic offline test will scan the drive's surface every 4 >> hours, correcting soft errors and remapping any bad sectors that could >> still be read. > >Well, the manual off-line test didn't do anything helpful about >correcting errors when I tried it. It discovered some, but that was >all. If the error is correctable (the data could be read) then the disk will rewrite the data and remap the sector if it is bad. If the data could not be read, then the sector is put in a list of offline-uncorrectable errors and the sector will be reallocated the next time it is read. When the off-line long test (not the short one) is run, it has been more than 4 hours since the last test. The advantage of the automatic offline test is that it sees each sector frequently, and may be able to rescue the data before it is lost. What you did is not comparable. It's rather more like the difference between taking your car in for scheduled routine maintenance and waiting for it to break and then getting it fixed. Much more may be wrong in the latter case, and it may not be fixable. ... >I'd been giving a few duff drives a while back. Things like that are >always useful to experiment with. I did find that using dd if=/dev/zero >of=/dev/hdb to write to all sectors on the drive caused the drive to >sort itself out. Afterwards it passed the SMART check with flying >colours. This is not the same as a low-level format. What you did used some of the spare sectors, leaving fewer spare sectors for remapping in normal operation, and requiring a long seek for each spared sector. Doing a low-level format with the manufacturer's utility skips bad sectors in-line, with no long seeks, and makes a full-size spare sector list. >The drives have, since, also been reliable in two test boxes with FC4, 6 >& 7 over several months. ... ... Having sectors go bad is normal for modern hard drives, both because of their high density and their large number of sectors. If sectors go bad at a low rate, it is simply a waste to replace the drive with one that will hopefully perform the same way and not just fail early. -- ____________________________________________________________________ TonyN.:' <mailto:tonynelson@xxxxxxxxxxxxxxxxx> ' <http://www.georgeanelson.com/>
