Re: VmWare?

no.spam@xxxxxxxxxxxxxxxxxxxxxxx wrote:
On Mon, 05 Jan 2009 11:57:25 -0500, Jack Crenshaw
<jcrens@xxxxxxxxxxxxx> wrote:

Steven Hirsch wrote:
Jack Crenshaw wrote:
Steven Hirsch wrote:
Jack Crenshaw wrote:

I went through all the usual backup schemes, from floppies to tape backup to Zip drives. Got burned more than once by a Zip disk that corrupted itself, sitting in a box.
Jack,

Try the backup method of Champions: Digital Linear Tape (DLT).

Not sure how much data you need to have on-line at a time, but 70GB DLT IV drives are a $30.00 item on eBay with tapes a dime-a-dozen. Buy two or three drives and a box of tapes and go for it.

Some years back, I established a simple scheme for rotating backups over a small number of tapes and have yet to lose a single byte. DLT drives are extremely reliable and the tapes are rated in the tens-of-thousands of passes.

Hm. Isn't that the same as the old Colorado tape system? They look a lot alike.
No, not even close. The Colorado drives were DC2000 cartridges, IIRC. The 'DC' style cartridges were configured like an audio cassette and had two internal reels. The drive used a capstan shaft pressing against a pinch roller built into the cartridge to maintain constant linear velocity.
Smile! Reminds me of the old "Stringy Floppy" drives from Exatron. I had one on my TRS-80.

Not close as the stringy was endles loop. Nor were they long lived.

This is not to suggest, mind you, that the DLT drive is just a glorified Stringy Floppy. It's just that your description rings a bell.

The Stringy Floppy used a tiny (1/16" wide) tape on a single reel. It was a continous-loop tape -- tape came off the outside of the reel, went back in to the inside. I guess that's the same arrangement as the old 8-track audio tapes.

The tape cassettes were _TINY_, and the drive itself not much bigger than a cigarette pack.

You didn't buy Stringy Floppy tapes by capacity, but by time. You could get 1 minute, 5 minute, 10 minute, etc. That's how long it took for the entire reel to spool around.

Imagine a disk drive with a spin rate of 1/20 minutes, and you get the picture. Planning ahead was always a good idea.

The SF is long gone, of course. Still, it was a cute gadget, and while slow, it was infinitely more reliable than Tandy's floppy drives. I had a TRS-80 with Level I Basic, the all integer version. Later I upgraded to Level II Basic(read: Microsoft) and added the expansion interface and floppy drives. The drives were so incredibly unreliable, I ended up ripping them out, throwing away the expansion, pulling the Level II ROMs and going back to Level I with Stringy Floppy.

As a matter of interest, the software was written by Li-Chen Wang, the same guy who wrote Palo Alto Tiny Basic. Both bricks of software were masterpieces. Disassembling them was sort of like touring the Louvre. The tape used Manchester encoding, which allowed a baud rate of a "whopping" 14 KHz. Wang did a precise clock count on every Z80 instruction in the read-write loops, so that every path through the loops took exactly the same time. That's how he got square waves, and maximized the baud rate. A very nice piece of work.

I guess few people know this, but the TRS-80 Level I Basic _WAS_ Palo Alto Tiny. "All" Tandy did was add the device drivers and expand the math to floating point.

Funny I though it was more like LLL Basic. Another great peice of
code that helped inspire.

Nope. Being ever the curious type, I disassembled Level I Basic. About 1/3 of the way through, I thought "Say, this code looks familiar." Dragged out my Dr. Dobbs annual, and there it was. The same exact code, except for the floating point math and device drivers. I reckon that's why it was 4k instead of 1k.

You might appreciate this story. When I first got the TRS-80, I called up Tandy and got a VP in charge of software. I really hated the idea of being restricted to Basic, so I asked if there was some way I could get to the guts of the machine. He sent me a preproduction version of TBUG, which was their hex debugger. Later I got an assembler and disassembler. I almost never did anything in Basic, except for silly graphics demos.

All this was done using the Cassette drive. No floppies, at that point. I _HAD_ to know: How did Tandy and those other guys make a tape that would bypass Basic?

Turns out, they called a subroutine to read the tape. It would read the tape into RAM, then return. The tape format was similar to many obj formats, with target addresses for each block.

Because they knew the interpreter, they knew where the stack pointer was pointing when it called the tape read subroutine. The last block on each "system" tape poked a different address onto the stack -- the address of the loaded code. The RET instruction then jumped to their program. Cool.

Natch, when I got Level II Basic, I had to disassemble it also. My first reaction was "bleahhh!" Where Wang had lots of simple little, nicely structured subroutines, with a neat parser structure, L2 Basic was all one big bowl of spaghetti. It almost seemed that MS went out of their way to complexify it (maybe they did, to confound copycats). They had a lot of code that did nothing except build tables of addresses. Instead of calling subroutines, they would jump to the jumps. We're not talking about jump tables here; not a matter of indexing into such a table. These were just plain jumps to jumps. The addresses were fixed, but still indirect. I guessed that this was so they could hijack the jumps if they wanted to, but it struck me as nauseating. No tape reader subroutine ending with a RET, therefore no way to use the L1 tape trick.

Jack


Jack




DLT drives are descended from a DEC TZ-something format and have nothing in common with the DC series. They are roughly square in form-factor

Aka TK50 at some 90MB then TK70, and on and further. The most
expenive was a DLTIV jukebox system at something around 125k$
but it did put in tapes automajiklly from a a large rack.

I still have a Colorado 250 Travan.

Allison

with a single internal reel. The drive engages a hook and pulls the tape into the mechanism which contains its own take-up reel. There is no pressure roller in the system. The tape runs over a series of roller bearings for guidance. Constant linear velocity is maintained by a servo arrangement that modulates motor speed and direction as the tape pack changes size.

I just did a Google and found some drives. I can't decide though. Should I get the $5000 model or the $25,000 model? Decisions, decisions.
You're not looking in the right place. You shouldn't have to pay more than $50 + shipping maximum from eBay. I've bought perhaps a half-dozen of these in the last two years and have yet to get a clinker. They have a SCSI-2 interface and will cooperate with, e.g. Adaptec or NCR-descended controllers. The units seem to be retired from service due to insufficient capacity rather than wear - at least that's my guess. All to my gain. I don't mind changing out tapes once or twice during backup.

Steve

.

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