PIP, DUP, DIR & RESORC

I just recorded an hour of video on my 32GB iPhone5 and there’s nothing remarkable about that at all.

But, you know, 32GB is a huge amount of storage capacity. The book, “The Innovator’s Dilemma”, tracks the development of disk drives, the disk drive industry and the impact that new technologies have on the dominant incumbent manufacturer… it’s worth a read if you’re that way inclined. No, really, it is.

But 32GB pales into insignificance with the kind of capacity from our storage solution providers such as NetApp. They provide two types of storage solution for corporate data, one that uses spinning disks and one that uses solid state “flash” drives, somewhat akin to the type of thing in my iPhone, and laptop.

For example, NetApp’s FAS2500 Series supports both traditional spinning disks and flash drives as a hybrid solution. The FAS2500 series is aimed at “entry-level” enterprises, branch offices and remote locations and can provide up to 2.3PB (Petabytes) of storage.

Now that’s a pretty impressive number. 2.3Petabytes is 2,300,000Gigabytes, or 2300,000,000Megabytes or 718,750 of my 32GB iPhones (if I’ve done my maths correctly).

But even that doesn’t come close to the larger models from NetApp. The enterprise-grade FAS8000 Series can provide 3,218,750 32GB iPhones worth of storage (103Petabytes, or 103,000,000Gigabytes).

This is mind-blowing stuff, although I suspect that we mostly take it all for granted. But when I were a lad, things were different…

Back in the day when I was a computer engineer, the first systems I worked on used DEC’s PDP 1103 processors coupled to PERTEC disc drives. The disk drive units offered 20Megabytes of capacity. 20MB is 0.02 of a Gigabyte, or 1/1600th of my iPhone’s capacity.

And there was no way you could fit one of these into your pocket!

A typical Pertec disk drive

A typical Pertec disk drive

As you can see – the drive unit fits snugly into a standard 19inch rack. Each disk is about the size of an LP. For those that don’t know, an LP was a round black plastic disc mainly used for recording and playback of music, but that’s a whole other ball of wax. The creamy-coloured round thing is a hard plastic cover for the removable disk, under which were 3 more fixed disks, each disk offering 5MB of capacity.

The disks themselves were made of aluminium, and were coated with a magnetic layer onto which was written, and from which was read, the files needed to make the whole thing work. The “read/write” heads were at least the size of a modern day penny, and floated just above the surface of the disk. “Just above” means that a human hair would be an insurmountable object, should one get in the way.

RK05 read/write heads

RK05 read/write heads

When operating, the whole unit would shake, rattle and roll, with the read/write assembly attached to a huge “voice coil” moving backwards and forwards over the disks as shown in this video:

 https://www.youtube.com/watch?v=ByLp9A1nn7U

Slow by today’s standards, and with such limited capacity as to be useless now, they were however excellent products for getting to grips with how computers work, and were pretty much indestructible.

Cats’ eyes, hexes and oscilloscopes

These RK05 disk drive units had to have regular preventative maintenance visits. Part of this procedure involved using a special removable disk called a “cat’s eye” pack and an oscilloscope and some hexadecimal command to precisely position the read/write heads. If they were out of position, then a dual-sinusoidal wave on the oscilloscope would be out of balance or phase – image a squinting cat staring at you, one eye larger than the other (hence “cats eye” pack).

To get the cat’s eyes the same size, you had to use an allen key on a grub screw on a v-shaped wedge to gently move the read/write assembly backwards (or forwards). Having perfectly accomplished this delicate manoeuvre, I tried to extract the allen key, but my fingers slipped on it, and it disappeared into the innards of the drive unit.

The voice coil was effectively a huge and powerful electromagnet and the allen key, being made of steel, was stuck to its underside.

This presented me with a dilemma: there was no way to get to the allen key without shutting down the system, but I couldn’t shut the system down without first removing the allen key.

So I did the only this I could do, which was to switch the computer off, and hope for the best. Fortunately, as the heads retracted, the electromagnetic voice coil lost enough of its magnetism to allow gravity to overpower it and the allen key dropped to the base of the cast aluminium drive unit.

Then it was a simple matter of disassembling the drive so I could extract the allen key, then rebuilding the drive unit, then cleaning the heads and disk with copious quantities of isopropyl alcohol, then rigorously checking for signs of a head crash, and finally realigning the heads, taking extra care not to drop the allen key…

The Incident of the Hot Salt Beef Sandwich at Lunchtime

Having mostly finished another preventative maintenance visit at one of my customers in StJames’ Square, London, I was taking a well-earned break, and was chatting on the phone to a girl while munching a hot salt beef sandwich from the local deli.

The lid of the disk drive unit was open and as I bit into the juicy, tender and tasty beef, a gobbet of fat shot out from between the slices of rye and landed smack onto the disk, which was spinning at 3400rpm. Grease went everywhere.

I hastily hung up from the call, and once again had to take decisive action. At least I could power this one down properly, but even so a lot more isopropyl alcohol was used on the disassembled parts to get rid of all the gunk, and again it was a painstaking and time consuming process to rebuild and check everything.

Get out of jail card

Every so often, once in a blue moon, there’d be a problem that just could not be resolved on site. Sometimes you’d just be stumped, nothing made sense, all logic went out of the window and none of the standard procedures worked.

For occasions like this, we had a special get out of jail card. It wasn’t deemed good enough to say “I don’t know” to the customer. When their valued call logging system wasn’t working, what they wanted most was reassurance that everything was going to be all right.

It’s like going to the Doctor’s with an illness – as long as you’re given a label, you’ve got something, an “itis” for example. That “itis” leads to acceptance and acceptance leads to confidence that something can be done. The problem has been given shape and form and remedial action can be taken.

On occasions like this we dug deep into the disk drives’ highly technical manual and made use of the most arcane aspect of the manufacturer’s soul. The diagnosis that we gave any unfixable problem on site, complete with much car mechanic’s tooth sucking, was: “I’m afraid it’s a sector phase lock loop problem, this has to go back to the lab”…

Then it was just the question of getting that huge and heavy disk drive unit into the car, without putting one’s back out.

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(originally published under the title "Memories are made of this" at www.silverbug.it. PIP, DUP, DIR, RESORC were commands used to rebuild  minimum bootable system)