Saturday 11 February 2012

Data recovery

I used to do a lot of this, 25 years ago, and I still do an occasional one.

I decided to go through my old floppy disks, vintage about 25 years ago, with all the various articles and correspondence. I did this a while back, and pulled off a bunch of stories, which you can find on my web site. But I was going to get everything this time.

They're all on 5 1/4 inch 360 kb floppy disks. These days, most computers don't even have a 3 1/2 inch floppy drive, and 5 1/4 drives are dead as a dodo. That's why I need to get this sorted out, whike it's still possible.  But ... I still have one, I remember hanging on to it. So I went into the top room, and found it fairly quickly. I didn't fancy setting up a Windows computer, and if I just booted off Dos, what would I copy the data to? So I put it into a Linux box, which I had linked to my network. It was pretty easy to install, and I knew that I couldn't just put in the floppies and read them (like you can with Dos), I had to mount them. So I did that. I found about 20 diskettes, labelled 1 to 19 and 28 to 32. I wonder where the others are? So I started copying.

After about a dozen, I started finding that the diskettes wouldn't read. And neither would the backup diskettes (in the same boxes). And I thought, huh, 25 years is a long time, they've deteriorated.

And then I had dinner, and did some other stuff, and my UPS crashed (see other blog), and I forgot about it for a bit in the hectic process of recovering from that.

When I woke up this morning, I woke with an idea. The diskette drive I've been using is a 1.2 mb drive, and that read/writes 80 tracks of 15 sectors per track. But the 360 kb drives I wrote the disks with, used 40 tracks of 9 sectors per track. And because there's twice as many tracks, the tracks are narrower, and so is the read/write head. So maybe, I thought, if only I still had a 360 kb drive, it would read them? Because the read-write head is better matched to the tracks on the floppy. This is actually something I've known for, well, 25 years. When you're in data recovery, it helps to know things like that.

So I went out to the shed, where I keep old computer bits, and rooted around, and I found Dobbin! Dobbin was a computer we used as an old workhorse. It had a full length 10 megabit ethernet card, which I picked up in a job lot really cheap and was the basis for my first ethernet network. It had a full length video card, which would be able to  do monochrome text and nothing else, and a full length hard disk controller card, connected to a 10 megabyte hard drive. Yes. 10 megabytes. These days, you put 1000 megabytes of memory in a computer, and hard drives are a million megabytes.

And it had two floppy drives. I knew they'd be 360kb, because that's all that was possible in that ancient a computer. So I pulled out the drives. They were ... manky. 25 years of sitting idle had left them filthy, greasy and horrible. So I cleaned them up with a bit of alcohol, and installed one of them in the linux box. And it was just what the doctor ordered (the disk doctor, that is). I was able to read all the floppies very nicely, and put the files onto my network. And I also found the box with the missing diskettes numbered 20 to 27.

So now I'm going to go through all that data, and de-duplicate (I see some files are there multiple times). Then I'll weed out the useless stuff (there's some Dos programs there, not really of interest). And I'm thinking I might make a Kindle book out of it all.

What's there? There's the fiction stories I wrote, and the technical articles for the magazines, some correspondence and some product reviews.

And on one disk, I found a version of Findvirus that was able to find 15 viruses! 

"Version 5.1 - includes Boot Sector Viruses: Ashar, Brain, Denzuk, Italian, Pentagon, Stoned and Yale
and file viruses 405, 648, 1168, 1701, 1704, 1813, 2086 and 3066."

The algorithm was absolutely awful; this was before I did the Big Rewrite that made it go like the clappers.

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