[QUOTE=cheesehead;355183].Amazingly, [I]computer hardware does fail![/I] It was happening before I was born, it happened all through my working career, and it still happens now. It's not magic. :-D[/QUOTE]

Sorry, I wasn't quite clear. What I meant was the people didn't think it was possible for a hard drive to recover from the click of death.

[QUOTE=TheMawn;355185]Sorry, I wasn't quite clear. What I meant was the people didn't think it was possible for a hard drive to recover from the click of death.[/QUOTE]Well, disks do have some spare tracks that can be used when a single, or small number of, tracks fail. The hardware's firmware takes care of that without user notification, usually.

It's sorta like exchanging a flat tire with a spare -- doesn't heal the flat tire's damage, but allows continued overall vehicle operation for a while with the spare in its place. Except that on the disk, the physical tracks can't be moved around, but the controller can make a note to itself: "Whenever there's an operation request for track 1123, use track 8879 instead."

(That's what happened on one of my HDDs. It was in the shop for one repair, when their routine diagnostic noted that the HDD was using a large percentage of its spare tracks. The HDD was still usable, but with a smaller and smaller margin of spare tracks. I agreed with the shop's recommendation to replace it with a new (faster, larger) HDD after copying all partitions from old to new.)

Of course, a "click" probably involves more than a couple of bits dropped on a track.

Good info!

As for the drive letters... I take out the old drive, put in the new, drop everything into whatever partitions I make and them rename them to F: and Z: and everything should be back to normal?

[QUOTE=TheMawn;355195]
As for the drive letters... I take out the old drive, put in the new, drop everything into whatever partitions I make and them rename them to F: and Z: and everything should be back to normal?[/QUOTE]Maybe I should just say that if renaming works for you, that's fine and dandy.

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The following might be confusing:

If the old and new disks are not mounted on the same system at the same time (i.e., you're copying data to the new disk from a backup rather than directly from the old disk, and the backup isn't an F: or a Z:), you can have F: and Z: partitions on the new disk right from the start.

Actually, F: and Z: are just virtual names for the operating system to use. The disks have [I]labels[/I], like "DATA1" or "XYZ" which are real names written on the disk when it's formatted, that they carry around when you dismount and move them, but they don't actually carry around the F: and Z: designations. Those are assigned by the OS when the disks are mounted (or the system is booted).

Often, a certain physical "slot" for a disk (or partition) will always have the same letter designation by the OS, and whatever physical disk is mounted at that physical position is designated E:, for instance.

Windows assigns letters in a certain fixed order. C: is the first HDD, D: is the second, E: is the third, and so on. If a disk labelled DATA1 is in the second "slot" and a disk labelled XYZ is in the third slot, Windows will show that D: is DATA1 and E: is XYZ. Now, if you interchange those two disks, Windows will show that D: is XYZ and E: is DATA1.

Somewhere around here be dragons:

Partitions on an HDD are each treated like a separate physical disk _for purposes of assigning letters_. But of course you can't physically interchange their positions on the HDD, so Windows will always give the first partition a letter, the next partition the next letter, and so on. (This isn't strictly true, but I won't clutter up with the esoterics.)

So, you could have both the old disk and the new disk on the same system at the same time, and have F: and Z: on the new disk, as long as the old disk uses letters other than F: and Z: for its partitions. If it's Windows, AFAIK it will assign letters based on the physical "slot" each disk is in and the order in which each partition is placed on each disk -- this will always result in different letters for different disks or partitions. I don't know what other OSes do, but I'd bet they also assure that each different disk or partition has a different letter, no matter how they're assigned.

It was all so simple and logical when I didn't try to explain it to someone else.

Well, you most probably have in your house a clean, furnished, wooden desk, and a package of playing cards. If you don't have the desk, the marble floor in the bathroom or kitchen will do it. If you don't have the playing cards, a credit/debit bank card will do it, but for that you must bent it few microns before (the playing cards are already bent by factory, they are not straight, contrarily to what most people believe).

Pick any playing card from the package and put it face-down on the table. Hit it with a flip (flick?) of your finger in such a way that it is sliding on the face of the table, and dosage your force in such a way that it will move about 30 or 40 cm. Repeat few times.

Turn the card upside down (face-up). Hit is with the same force. Amazing, this time the card will "fly" from the table, or move many meters on your marble floor, seeming like flying, or hovering over the ground.

If your floor (or the surface of the table) is not [U]perfect[/U] straight and shiny, then the card [U]will[/U] indeed fly, eventually making a loop into the air.

This is called in aeronautics "the ground effect", and it happens because the card is not perfectly flat. When faced-up, the margins of the card are few microns "over" the ground. Therefore, when the card slides on the table, air goes under, and the card is moving frictionless on the table, on a microscopic blanket of air.

If the surface of the table is not perfect flat and shiny, if it is scratched or if some impurities goes under the card (think a grain of salt), then this blanket is disturbed, and the card "jumps", like an exploding car.

When we were children, we used to play this trick on another children, we had a piece of oval iron flat, we put it on the desks at the school and we flick it, betting who can flick it further away. The trick was exactly the same, one of us had an older brother who revealed the trick to us, the piece of iron wasn't perfect flat, and if you knew how to place it, it would go much further. When we hand it to the next guy, we turned upside-down, so he could only launch it half of the distance, even if he used all the force of his finger flick.

Your HDD head works exactly the same. There is a small "playing card" which is called "head", and it reads the information from the disks. In case you don't know :razz:

The area of the head is about 1 squared mm, but don't imagine the track is so wide, otherwise your harddisk would only be able to store few couple of bytes. The track is microscopic, there are thousands of tracks per inch, but the head is still 1 squared mm. That is because there is no mechanism to "lift" the head over the surface of the disk, as it was for bigger and older disks. The head is reading the tracks by magnetic influence, same as the head of your tape player, but the HDD head should not stay in contact with the plate of the disc, otherwise the friction between the head and the plate will damage the disk in few days, from both mechanical friction AND electrostatic charging (due to rotation, think Van der Graaf machine). Therefore, the head "hovers" few microns OVER the surface of the disk, and there is no mechanism to control this distance, beside of the "ground effect". It is very difficult to control it mechanically. Therefore, the "huge" area of the head is not used to read the track, but to do the "aeroplaning" (well, think "aquaplaning" that happens to your car on a wet street, it is exactly the same phenomenon, but produced by water, when your tires are not properly maintained). Reading the track, the "active" magnetic part is just very small in the middle, microscopic. The rest is "playing card". One full square millimeter of playing card (huge area, compared to active area, think a playing card with a 5-mm-diameter dot in the middle) it is used to "lift" the head over the surface. Due to very fast rotation of the disks, air goes in between the head and the plate, and "lifts" the heads up. Yes, there are more heads, two for each physical disk, one for each side. You can have from 2 to 14 heads inside, depending on your hdd. That is the mystery why new, small (in physical dimension, not in storage space) disks have a hole somewhere, equipped with an air filter (have you ever opened a HDD? there is a small air filter inside which looks like a miniature pillow) they need to "suck" air from outside to work properly. Contrarily to the belief, they are NOT airtight (as the old, 5 inch or 7 inch HDD used to be).

In their quest to reduce the dimension, to increase the density (more physical disks in the package, therefor increasing the number of faces, but decreasing the space in between), reduce the price, etc, the manufacturers opted for "aero-planing" heads. The disk contains special "landing zones" (think like airports in real life) from where the heads "take off", when the disks start to spin, due to ground effect. Special form of the head (think playing card) and the air filters favor this. Then the head is "hovering", flying, over the surface of the plate, at only few microns distance. This way, there is no friction, and the disk can work for years.

Now, think about the air filter malfunction. This is the most frequent cause of HDD crashing. You will not read too much of this on the internet. People still believe that the HDD is an ermetic (air tight) closed structure, where the air or moisture can't go. That is false. You can google for "hdd air filter". I never saw a hdd malfunction in my life which was not related to air filtering. And I opened and analyzed hundreds in the last 14 years.

From time to time, a particle of dust escape the filtering mechanism, and goes inside. Sooner or later, this particle of dirt gets between the head and the plate, therefore disturbing the air blanket. If the particle is enough big, the head will "crush" it, therefore causing a "scratch" on the surface of the disc. A microscopic scratch.

But this is not necessary. The particle may be much smaller, so it does not touch and does not scratch the surface of the disk, it does not touch the head either, it just "fly" between the head and the surface.

Well, bad news! This is enough to cause a small vibration on the head, which may eventually transmit to the head above (the opposite face of the other physical disk, which has its own head, the heads are coupled together, as a comb that goes between the plates, each finger of the comb has heads on both sides, to read both plates, you can google for disk images). The small vibration will cause the other head to "hit" the disk, (its own disk) causing a small scratch on that disk.

Next pass of the head over the scratch, and the heads hits the scratch, causing a vibration, therefore hitting the disk again, in different place (because the disks rotate in this time).

Some British lord, I forgot his name, had a funny law about how your boots get dirty, and how you all get dirty, when you go hunting. One small piece of soil spill on one of your boots, then you walk and the boots touch each other, therefore the other boot will have some dirt, then the boots touch again and now you have four spots, and after a while, all your hunting trousers are dirty on the inner side, you have a "mersenne number" of dirt spots on your legs, your hands, your face, etc.

This happens with the harddisks too. First you have a small scratch. Some bytes lost because the head vibrates every time it hits the scratch, and during vibrations the magnetic field varies (as distance to the magnetic plate varies) and it can not de-cypher the encoded information anymore.

Hitting the scratch causes the "clink" you hear. This also damages the head a bit, and in turn, the "landing zones" are damaged. Imagine a B77 landing with a broken wheel, the track of the airport may not take that very well... It may take days, hours, or years till all the disk is completely damaged, as the heads can't "take off" anymore. But when it happen, it happen fast, the damaging speed is exponential, and you can do nothing about it.

The best is to [B][U]back-up every important bit of information, as soon as you can, and as fast as you can[/U][/B]. If you have no money to replace the disk, then do it on the web. Lots of providers, amazon or google included, offer now enough GB storage for free. Put everything on encrypted zips, and find some cloud where to drop them. FAST! Don't wait till you have a new hdd. And don't ask me how I know! [SUP](TM)[/SUP] :razz:

As your data is obviously very important to you, when replacing the disk can you use a RAID array, to make future problems that bit easier to sort out?

Consider cooling your new disk if it is going to be heavily used.

@ LaurV- Great explanation! Thanks!

@ The Mawn- If you encounter difficulties with your data, post about it. There are recovery possibilities. Some techniques are quite surprising, but have worked for me on a disk and data I had given up for lost.

Alright. Thanks for the information people.

As of right now, the disk is still working fine. I've topped off the backup I already had of the users partition. I won't be able to move the SSD image anywhere since it's too big but that will only be a problem if the SSD and HDD fail at the same time.

I don't think I'll bother with a RAID array. I'm looking at saving myself the expense of a single hard drive if this was in fact a one-and-done random hardware malfunction, so I doubt that I'll look into a RAID array.


Cheesehead: Thanks for the partitions explanation. I'll try renaming the partitions to F: and Z: and see if that works. If I have to, I'll re-move all the users folders etc to that drive.

[QUOTE=TheMawn;355248]Alright. Thanks for the information people.

As of right now, the disk is still working fine. I've topped off the backup I already had of the users partition. I won't be able to move the SSD image anywhere since it's too big but that will only be a problem if the SSD and HDD fail at the same time.

I don't think I'll bother with a RAID array. I'm looking at saving myself the expense of a single hard drive if this was in fact a one-and-done random hardware malfunction, so I doubt that I'll look into a RAID array.
[/QUOTE]

It's just handy if you have if you have one drive fail, you can replace it without much hassle. That's all. RAID has saved me from restoring twice already.

[QUOTE=Mark Rose;355267]RAID has saved me from restoring twice already.[/QUOTE]

Completely agree.

I personally only order enterprise class "kit" with at least four "hot-swap" hard-drives, and configure them all in a RAID6 configuration.

It is always entertaining to suddenly bring two of the drives off-line unexpectedly, and demonstrate that the system continues to work....