[sclug] My disk esplode

David Given dg at cowlark.com
Tue Apr 15 00:11:40 UTC 2008

Dickon Hood wrote:
> : At this point I needed to take an image of the hard disk. dd would not
> : work, because dd doesn't handle I/O errors appropriately.
> dd if=... of=... conv=noerror,sync
> Bad blocks are replaced with zero bytes, and it all works as well as can
> be expected.  Likely one of the two tools you mention below do little more
> than this.

Ah, I didn't know the sync option caused it to replace the bad blocks
with zeroed blocks --- noerror alone just omits them, with catastrophic
results on disk images!

ddrescue is actually fairly clever; it will as rapidly as possible read
the working parts of the disk, and then binary chops the non-working
bits down to individual sectors and will keep retrying them until they
work (or you tell it to stop). It also keeps ongoing logfiles so it can
resume where it left off if you tell it to stop. Dead handy.

> It's quite simple, people: one copy of the data is no copy at all.  You
> have no backup, and you have no guarantee that the data you think you have
> is available.

Indeed. But I *am* a home user, not a professional one; the data is not
of monetary worth, merely inconvenient to replace; and I don't want to
pay twice as much for my disk space (although that's less of an issue
these days). This was the first disk I've *ever* had that's died. Also,
RAID over USB is a pain in the arse.

If the SMART had worked, the disk would have moaned at me *before* it
went wrong and given me time for me to do something about it. I suspect
I may invest in a SATA external card and then buy SATA disks in future.
Faster, too...

(Incidentally, please don't cc me when you reply to the list, people; I
don't need two copies...)

???? ?????????????? ????? http://www.cowlark.com ?????
? "I have always wished for my computer to be as easy to use as my
? telephone; my wish has come true because I can no longer figure out
? how to use my telephone." --- Bjarne Stroustrup

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