The Big Disk

Copyright Dr Alan Solomon, 1986-1995

Summer was almost over; you could tell by the way the computer shows crawled 
out of the woodwork. August is a slack month in the computer industry, but 
not for us disk quacks. All over the country, people were doing their 
pre-holiday backup, and accidentally wiping out their hard disk. Other 
people were coming back from Teneriffe, and finding that two week's disuse had
made their disks stop working. I was quacking disks all over town, from 360K
 floppies with a few word processing documents right up to a 130 meg monster
that had been used as a LAN, and hadn't been backed up for three months. The 
guy who ran it was six inches ahead of a lynch mob when he reached me.

The rush had died down a bit, and I was just sitting in my office, chewing on a
 wine gum and wondering what Janet was doing. I often wonder what Janet is 
doing; she certainly doesn't know, and I feel that one of us should. Still, I 
didn't hire her for her ability to file, so I suppose I shouldn't complain. I 
was just poking about looking for a pink one, when the phone rang. I put the 
bag of winegums down, and answered.

This one was a doozy. There were two disks that had gone down at once, a 20 
meg and a 30, in different computers (both Tatungs); could I help? I made the 
usual non-committal noises (how can I tell until I've seen it?) and told the guy 
I'd talk to him later, as I had to go out and look at a disk.

By the time I came back, there were two parcels in Jan's cubbyhole. Jan was 
there too, which made the place a bit crowded, so I asked her what they 
were. "Disks", she said. I could see I
wasn't going to get anywhere with her, so I unwrapped the parcels. Inside, 
there was a 20 meg Seagate ST225 (probably the commonest disk in the 
world) and something I'd never seen before, but which looked large and 
sleek and full of bytes. I phone the number that was on the disks, and had a little chat.

"First of all", I said, "we'll need the computer that they went down in." "Oh, 
you won't need that," he said, "It's a bog standard AT clone." I could see 
that I was dealing with an immovable object, so I just said "OK, I'll have 
a go".

I put the 20 meg into my AT clone, and couldn't get it to respond at all. Not 
surprising, really, since my controller was probably different from his. So I 
phoned up the Tatung and told him the bad news. "I'll need your Tatung, and 
your controller, and your DOS".

Next day the Tatung turned up, minus a keyboard, monitor and DOS. But at least
the controller gave me access to the disk, and it turned out to be a fairly 
straight forward case of several bad sectors on the disk, making the 
directory and File Allocation Table unreadable. I patched things up, and 
then I wanted to put the precious data onto a good disk. I put it on one of 
mine, and got Jan to phone up the owner, to ask for a new disk. What I say is, 
you don't give a disk a second chance. If it has lost your data once, it could do 
it again, and this time I might not be able to get it back. And anyway, a new 
disk only costs #200 or so. He agreed, and said he'd send me a new disk.

About a week later, the new disk arrived. I put it in the Tatung, and 
tried to make it work. I spent three hours wrestling with that thing, and in
 the end, I decided that it wasn't my job to make a new disk work. Probably, 
it was not compatible with the controller, so I phone up chummy and 
asked for another disk. "And while you're at it, could you send another 
disk just like the 30".

The big disk arrived, but not the 20. Looking carefully at the big disk, I 
could see it had 1000 cylinders, 8 heads and 17 sectors per track; it was a 68 
megabyte disk. Don't ask me why he was using a 68 meg as a 30, but mine is not
 to reason why, mine is just to quack hard disks. 

I tackled the big disk. It had a lot wrong with it; quite a lot of the 
sectors were unreadable with any normal means, but I don't use normal means.
I have a little program called "The Persuader" which can get data off disks
 that other disk repair programs give up on as impossible. I Persuaded this 
big disk a bit, and eventually stripped  off 99.4% of the files. There was some
 damage to the FAT, which even The Persuader couldn't handle, but a bit 
of applied Real Intelligence and a 
bit-shift or two later, and I had all but a couple of bytes of that 
all-important FAT.

Then I formatted up the new disk to receive the data, loaded it all on, 
and did a DIR. It didn't work. 

It's always depressing when you do everything right, but the disk doesn't