Imablog Perspectives of a Canadian in the Old/Deep/New/Geographic South: This is where I ramble on about nothing in particular and post a few nice pictures.

Hard Drive Dissection Part 1

You know what they say about idle hands...

Spent part of yesterday indulging my curiosity about the anatomy of hard drives with a couple of old hard drives sitting around being paper weights.

The first victimdrive to be disassembled was this old 3 GB Seagate Medalist (late 90s vintage).

This is what you see when the top cover is removed. I was a little surprised to see that the drive was only a single platter.

Older hard drives had what was known as a landing zone, an area of the drive platter without any data where the heads were moved to when the drive wasn't in operation. If the arm came loose during transport or impact, any damage to the platter would occur here and not on the data portion of the platter. On this particular drive, the landing zone is the inner portion of the platter.

The dark rectangular block in the middle is the lower read/write head. Looks like there are two, but the other one is just the reflection off the platter.

At first I couldn't figure out what the purpose of this black arm was, but then I figured out that it keeps the drive arm in the parked position over the landing zone. Air currents created by the spinning platter push the black arm out of the way so that the drive arm can move around. The white blob is some kind of filter. Clever.

This is a small magnetic clip that also helps to hold the drive arm in its parked position.

The hard drive motor and a view of the read/write head.

The drive platters are polished very smooth. Since the drive heads only float a few microns above the surface of the platter, a very smooth surface is essential.

All that's left is the drive arm and voice coil mechanism. The drive arm contains a copper coil positioned between two very very strong magnets (many geeks will harvest old drives to get at these magnets). Changing the current flowing through the coil creates a magnetic field that interacts with the magnetic field of the magnets and causes the arm to move. The top plate is held on magnetically, so removing it is simply a matter of prying it off.

This is the disassembled drive arm mechanism. You can see the two magnets (the parts that have the writing on them), which are glued to the top and bottom plates, and the copper coil at the end of the drive arm.

Coming up in Part 2: The innards of a 20 GB IBM DeathstarDeskstar

5

Earned a 5 gallon pin after donating blood today. 40 donations! Woo hoo!

Hard Drive Dissection Part 2

Continuing with the investigation into the inner workings of hard drives, the second drive is a newer, although just as broken 20 GB IBM DeathstarDeskstar.

Outside, it looks like any other 3.5" form factor drive

Looks pretty similar on the inside too, although there are a few notable differences in design. Again, I was a little surprised to find this drive was also a single platter design. Nearly 7 times the capacity of the old drive on the same sized platter.

Instead of a landing zone on the platter, this one uses a landing zone outside the platter. The heads are moved into the white plastic holder when not in use. Moving the landing zone off the platter frees up additional space on the platter where data can be stored. It also makes the platters much less susceptible to impact related damage.

Again, two very strong magnets and the voice coil (this drive uses a larger coil) used to move the drive arm.

Close up of the read/write head.

Some of the more significant differences are in the way the drive arm is designed. Here are the drive arms for the two drives side by side. The top one is from the old 3GB Seagate (from part 1), the bottom one is from the newer IBM. Note newer arm is made of much less material and is generally smaller. This helps reduce the weight of the arm allowing it to move around faster (decreasing access times). The IBM arm also has a much larger area coil than the other one.

The newer arm also has a much smaller read/write head than the old one. This means smaller magnetic domains can be created and more data crammed onto the platter.

Google Chart API

Google's new Chart API looks like it'll be fun to play with. The method for specifying values for the data points is a little unusual, but interesting. There are a surprising number of options you get to play with. I'm looking forward to messing around with it.

(Bonus) Hard Drive Dissection Part 3

This next one is a bit of a bonus. It's a 2.5" 60 GB drive that I pulled out of a laptop when it flaked out. Fortunately the drive managed to recover itself long enough for me to retrieve the data. I was using it for a little bit as an emergency backup/transfer drive in an external enclosure until the motor made loud shrieking sounds and finally seized up on me.

As you can see from this shot, 2.5" form factor drives are pretty small. This one has 3 times the capacity of the 3.5" form factor drive from Part 2.

Under the cover it's like a miniature version of the larger drives. Like the Deskstar, this one also uses an off-platter landing zone. This drive has two platters.

Unlike the larger drives, this one only has one magnet, presumably for space reasons. It's just as strong as the magnets in the larger drives though.

The fully disassembled drive and its two platters

A close up of the read/write heads, one pair for each platter.

Size comparison of two drive arms

I'm an uncle again!

Just got a call from Mom telling me that my brother and his wife are the proud parents of a baby girl as of yesterday.

Congratulations to them!

Update:

Jocelyn Francis Ellis Mah
Born January 4, 2008 at 7:12pm
Weight 3.713 kilograms (or 8 pounds 3 ounces)

Moving on to Fedora

After experiencing numerous inexplicable problems (not seeing anything connected to the USB ports, not finding the DHCP server, no sound...the list went on and on) trying to get Windows XP running on the home computer (with new e-Bay'ed motherboard), I decided to wipe everything clean and install Fedora 8 on the darned thing.

Wouldn't you know it, everything that wasn't working in Windows worked again. USB, sound, network, the works. It's almost like having a brand new computer. The only problem I ended up having was discovering a few things that got left off the backup I made. Nothing critical though.

Now I need to figure out how to get my PDA syncing, get Quicken up and running, and work on keyboard and mouse mappings.

Fedora transition

It's been a few days working with Fedora at home, and so far it's going well.

Unfortunately I'm not able to completely dispose of Windows since I still need to use Quicken and there isn't anything comparable available for Linux yet (that I've found anyway). Fortunately, thanks to the magic of virtual machine (VM) technology, that was one problem I was able to get around relatively easily. Downloaded and installed VirtualBox, followed the instructions to create a new virtual machine and booted it up with my Windows CD. Took a couple of days to get Windows and all the updates installed, but now I have a working Windows VM running in my Fedora install. This VM thing is pretty cool. A little slower than an actual computer, but not so much that it's unusable. Now I just need to figure out how to get the VM to grab USB devices so I can use my PDA and scanner to get things into Quicken.

Scanner joy

Took a few days of research on various web forums and tinkering around with the system, but I finally managed to get the scanner (Epson Perfection V200) working under Fedora 8. Now it's not a paperweight anymore! One more thing to take off the list. Woot!

In the hopes that this might help someone else who runs into this (or a similar problem), I'll describe what worked for me.

Started off with using yum to install the SANE packages, but didn't get anywhere with that. More Google and forum searching led me to the epkowa drivers (iscan-2.8.0-1.c2) so I downloaded and installed those. Got a little further, but still no joy.

Finally I uninstalled all the SANE and iscan stuff (which ended up uninstalling the printer drivers too, but those were easy to put back) and just installed iscan. That got me to the point where I could run iscan as root and scan stuff, but not as a regular user. Then I found a tip on a forum to edit /etc/sane.d/dll.conf and comment out the epson line. Finally, scanner joy!

iscan doesn't have nearly as many features as Epson's Windows software but it works, I can use the scanner and it's not a $70 paperweight anymore.

Summary (this is what worked for me):
- If you have sane/xsane installed, remove it with 'yum remove sane xsane'. On my system it also removed my printer drivers (hpijs and hplip), but they can be reinstalled afterwards.
- Download the latest version of the iscan RPM and install with 'rpm -ivh iscan-xxx.rpm'
- Edit /etc/sane.d/dll.conf and comment out the epson line. Make sure there's a line that says 'epkowa' and that it's uncommented.
- You should be able to run iscan from a terminal window or launch Scanner Utility either from the Applications menu or the desktop icon

Great big white water bowl

Simba's discovered that the two toilets in the house are great places to get water when he's feeling too lazy to walk over to the proper water bowl in the kitchen or use the water bottle in his crate.

One problem is that he's a really messy drinker, and ends up soaking the mats and dripping all over the place.

The other problem is that I usually put those Clorox toilet tabs in the tank to help keep things clean. Probably not too healthy for him to be drinking the water.

One more reason to remember to keep the lid down.

PDA sliding downhill

I have a feeling I may be surfing E-Bay in the near future for a used T3 to replace mine. The digitizer on mine is starting to go wacky, and to get it to work properly, I have to squeeze the sides.

I suppose I could take it apart to make sure everything is connected properly. The T3's aren't quite as trivial to disassemble as the Visors were though.

Equipment testing marathon

This week I did surveys on:
2 angio labs
4 cath labs (1 biplane)
2 EP labs (1 biplane)
1 fluoro room
4 digital portables

all in preparation for the opening of the new hospital building. I still have two rad/fluoro rooms, 4 c-arms and 3 SPECT/CT scanners left to survey.

I'm pooped.

It will be interesting to see what this month's radiation badge reading ends up being.

Coming up

25-Jan-08 - Blogger meetup at Gene's Haufbrau.
26/27-Jan-08 - Charleston Kennel Club Dog Show and CSCLRC's Supported Entry

After all the equipment testing I've been doing the last two weeks, I could use a few beers.

The dog show is always a fun event to check out. The Lab Club's show is outside in a separate ring. Hopefully it doesn't rain on us like it did last year.

Bleh

Somehow I managed to catch yet another cold. I just got over the last one too. How annoying is that?

Bleh. Argh. Ugh.

Bloggers and Tweeters

Tonight's meetup at Gene's Haufbrau was a lot of fun

Chuck meets a couple of Tweeters

JJ, Dave and Mrs Dave

Heather and the Tweeters (hey, what a great name for a band!)

Jared made it!

Broken archives

Crap, the blog archives are broken. Figures I'd find this out on the weekend. With the dog show going on this weekend I won't be able to fix it until Monday. In the meantime you'll just have to settle for the front page.

Picture overload

I ended up with close to 400 pictures from the weekend's dog show to sort through. Took another 100 or so at the dog park today too. There are some pretty good ones in the mix. They should be showing up in the gallery shortly.

Random favourites

Some random favourites from the dog show

One of the rescue dogs from Wild Heir Lab Rescue

A yellow lab in the show ring

Taking a peek

Crate surfing

A yellow lab waiting for his turn with the judge

More pictures over in the Gallery

PET Shielding

Ever wonder what goes into shielding for a PET imaging facility?

No? Well, I'm going to show you anyway.

First you need to find a Qualified Medical Physicist (like me) to develop a shielding design for you. The shielding design gets turned into a set of blueprints for the lead contractor to work with.

Then you need lead. Lots and lots of it.

This is a layer of 1/4" thick lead sheet lining the floor. The strips cover up the seams between the lead sheets so that there are no gaps. Depending on what's underneath, the floor may require as much as 1" of lead.

For the walls, you'll need stacks of 1/4" or 1/2" lead sheet attached to 3/4" plywood, like these

Thinner lead sheets are usually glued to drywall, but that doesn't quite cut it for the thicknesses required for PET shielding.

The lead/plywood sheets go up like this

The sheets are also interlocking to eliminate the gap between sheets

Depending on what's on the other side of the wall, you'll need bricks too. This is a stack of 1" interlocking bricks. Sometimes your wall might even need up to 2" thick bricks.

This is what the brick wall ends up looking like

The bricks are screwed into the metal studs for support. Thicker brick walls require additional support and are usually constructed between two sets of studs.

Who wants to visit?

Here

(My outdoor thermometer says 3°C)

There

Why Blog?

LCB asks:

Why do you have a blog?

I first started keeping a journal because of Doogie Howser.

Yeah, I hear some of you snickering back there. Laugh if you will, but I always thought the computer journal thing at the end of each episode was pretty neat.

My journal started off as just a simple database using Appleworks on my Apple ][e. Then it changed to a series of notebooks (most of which have since been tossed out by my parents in the Great Cleaning they did a few years ago) during my undergrad and grad school days.

Now I blog.

To me, blogging is just an extension (a very public one at that) of journaling. To others it's something else, but to me just an online journal. Since I'm just really bad at picking up the phone and calling people (emailing and IM'ing too), I use my blog to let people know what I'm up to, talk about or show off anything interesting I encounter and spill out some of the random things that the voices in my head tell mecross my mind.

That's why I keep a blog.

Want

I want...I need... (a common lament thrown at us by a DM during my gaming days)

32 GB SDHC cards