hamachi@KIM (Gordon Hamachi) (11/16/85)
This amazing tale of disk recovery may help someone else out.
After spending hours laboring over the disk "foobar" I was alarmed and
dismayed to see the "Do you want to initialize?" dialog box. The standard
tricks I'd used successfully in the past didn't work:
1. Try inserting the disk repeatedly (non-repeatable errors?)
2. Try inserting in the other drive (alignment problems?)
3. Try turning the Mac off for a while (reset everything?)
4. Try warming up the bad disk (thermal expansion alignment problems?).
5. New system disk (bad software?)
It was time for Fedit. After carefully reading the documentation I browsed
the disk and found that the directory was screwed up in a big way. Time to
hand-patch? Yes, but first I had to make a copy of the disk, and experiment
on that. No problem. Fedit lets you read sectors from one disk and write
them to another. Unfortunately, my troubles were not yet over. There was
Bomb #25, out of memory, after only 20 sectors were copied. Oops.
After rebooting, an amazing and heartwarming sight appeared: "The disk
foobar needs minor repairs". Okay. And when the disks had stopped
spinning, there before my eyes was a resurrected disk. Actually, all it had
was the directory entries of my lost disk "foobar". Somehow, miraculously,
the directory blocks on my "trashed" disk were fixed as they were copied
to the new disk. They couldn't be read by fedit nor by the Mac's disk insert
handler, but they could be copied. How can this be? You tell me.
Reaching into the freeware toolbox once again, I pulled out MacClone 2.0
and used that to copy my trashed "foobar" onto a blank disk. Fortunately,
like Fedit, MacClone doesn't care if the disk is "unreadable". It goes ahead
and does its best anyway.
Viola! I mean, Voila! Four hundred thousand recovered bytes!
The moral of the story: sometimes you can copy things you can't read. If you
don't believe me, that's okay, I hardly believe it, but I still have the bad
disk and the recovered data!
Hmm, time to pay for some (more) freeware.
--Gordon Hamachialexis@reed.UUCP (Alexis Dimitriadis) (11/21/85)
> After spending hours laboring over the disk "foobar" I was alarmed and > dismayed to see the "Do you want to initialize?" dialog box. > [...] Somehow, miraculously, > the directory blocks on my "trashed" disk were fixed as they were copied > to the new disk. They couldn't be read by fedit nor by the Mac's disk insert > handler, but they could be copied. How can this be? You tell me. I've often had to play doctor (and sometimes mortician :-() to people's disks. A couple of tricks that worked: If you are getting I/O errors when reading a file or a disk, sometimes it helps to enter FEDIT and try reading through the file blocks. When you reach the block that gives the I/O error, read the adjacent blocks, touch them (e.g., by changing a character to itself), and write them back out. Then try reading the bad block again. If you are lucky, you won't get an I/O error (you may get garbage on the block, but you have the rest of the file). This worked on a disk that someone had sat on. Some versions of Macwrite will periodically create files that they can not read afterwards. The best thing to do is get rid of all copies of the buggy version, but such a file may be read by setting its mode to TEXT. There will be garbage where rulers and font changes used to be, and you'll have to put those back in manually, but at least Macwrite can read the file. (And then once I had to dump a file to the imagewriter using Fedit, screen by screen, so it could be typed in again. Sigh..) Disclaimer: I know very little about the guts of the Macintosh. If someone has informed instructions for the restoration of bad disks, could you step forth? It seems our disks have been dropping like flies around here. Alexis Dimitriadis -- _______________________________________________ As soon as I get a full time job, the opinions expressed above will attach themselves to my employer, who will never be rid of them again. alexis @ reed {decvax,ihnp4,ucbcad,uw-beaver}!tektronix!reed.UUCP
gijs@ark.UUCP (Gijs Mos) (11/24/85)
>> [...] Somehow, miraculously, >> the directory blocks on my "trashed" disk were fixed as they were copied >> to the new disk. They couldn't be read by fedit nor by the Mac's disk insert >> handler, but they could be copied. How can this be? You tell me. The explanation is simple. The errors on your old disk must have been caused by bad address marks or the like. If your copy program copies the good sectors to a newly formatted disk all address marks will be ok on the new disk. The sectors on the new disk corrosponding to the bad sectors on the old disk will not contain valid data however. Fortunately there is a lot of redundancy in the Mac's file system. If the bad block used to be in the directory the Mac rebuilds the directory. Gijs {seismo,decvax,philabs}!mcvax!vu44!gijs