My iMac 2.5GHz Intel Core i5 running Lion 10.7.5 has been misbehaving.
Applications freeze intermittently, with spinning beachball, necessitating forced shutdown. Starting up stalls or generates spastic startup, again necessitating forced shutdown. Sometimes resting the iMac for 30+ minutes resolves the problem, sometimes not.
I ran HD Recovery which indicated that the disk is OK. Following that everything seems to be running normally.

Queries:
• Am I looking at momentary glitch(es)? Or is my hard drive in imminent risk of croaking? (I'm guessing that the very fact that I can access Recovery HD is an indication that the hard drive is functional.)
• If the latter, how does one go about replacing the hard drive?
• If one has to send it out to a repair facility (none in town), how might one protect the information on the drive from unauthorized access?
•If it needs replacing, will I be able to restore my previous system and files from Time Machine to get back to the status quo (ante)?

Depending on the answers to the above, I'll probably have numerous further queries.

Many thanks in advance for any and all assistance.

• As you surmise the drive is functional, that does not mean there are not problems on sectors of the disk. Disk Utility > Repair Disk can tell you if there is as damaged volume structoure and may be able to make repairs. However the only definitive test of impending drive failure I know of is a Surface Scan. TechTool Pro or Drive Genius can do the honors there.
• Replacing the drive depends on what Mac you have. Other World Computing has some excellent online videos for most machines. If you have an iMac that may be a chore best left to a professional.
• Get a known good clone of the drive, then erase the drive before sending it in for diagnistics and repair.
• Yes. But cloning back from a clone would be faster.

I ran Disk Utility > Repair Disk in Recovery HD which did not identify any problems.

If the hard drive craps out, how would it be possible to "erase the drive before sending it in for diagnistics and repair"?

I have no clue about cloning. Time Machine would have to do for me.

Edit: In case it's of value, the internal hard drive = WDC WD5000AAKS-402AA0, 500 GB.

Well, it would appear that I'm well and truly screwed.
(And here I sit in the public library using a PC.)

After several hours of functioning normally, the original problem returned. Once again, I went to Recovery HD and tried to use Disk Utility > Repair Disk. This time it went as far as to note that the (main) partition appeared to be OK, then wouldn't go any further. In fact, the spinning beachball came up and wouldn't quit.
I did another forced shutdown.
When I tried to access Recovery HD again, it made it to the Apple and spinnning pizza, but after a short while the Apple switched to a circle with diagonal slash and the pizza kept spinning.
Another forced shutdown.
Then the attempt to access Recovery HD switched to trying to access Apple's Internet recovery -- which of course could not be accomplished (since I'm not online and couldn't get online without the iMac up and running).
So, now what?!

At this point it looks as though I'm going to have to resurrect my 13-year-iMac running OS 9 -- I should be so lucky.

It is no consolation, but at least you won't need to worry about any data on the drive when you send it in for repairs. I do hope you have good Time Machine or other backups.

Oh, I got lotsa backups on TM.

Latest news: I finally gave in/up and took the iMac to the local university computer store. They ran Apple's recovery diagnostics on it which indicated that everything (especially the hard drive and fan) checked out as OK. They ran a couple other tests, which came up normal. PRAM was also reset. Now the iMac boots faster and more reliably than before.

So, rather than having their techs dig into it in more detail, I decided to see if whatever has been plaguing it has been given the old heave-ho and brought it home.

The one thing that niggles is the possibility that heat may be the culprit in the wonky functioning (since often a literal cooling-off period seems to help). Intermittent issues are always a bugger to deal with.

Stick around for the next chapter.

Addendum:
I can only hope that the iMac is behaving much like one's pet.
Anybody who's had a vaguely sick pet which didn't need veterinary care urgently but refused to get better and who finally decided that a trip to the vet was in order gets to the vet's only to have the pet demonstrate wellness to the professional, who then collects a fee for pronouncing same and sends the 'malingering' beast home, said beast 'dew-clawing' its nose at the caregiver.
The ride/outing alone solves the problem. It happens a lot.

Might not be a bad idea to keep Activity Monitor running while you're using the iMac. That way you can see if the beachballing, should it recur, is correlated with an application hogging CPU cycles or system memory.

After my last post (ca 1 hour) the iMac crapped out again; couldn't even get to Recovery HD.
So back into the shop it went. I probably won't know anything for about a week.
At the moment I'm back with my old iMac which I just upgraded/updated to OS 9.2.2.

> At the moment I'm back with my old iMac which I just upgraded/updated to OS 9.2.2.

Wow... Talk about reverting!

I'll be curious to hear about the experience.

From that description, based on much experience, 85% of the time I would call that a HDD failure in progress.

If you have your apple hardware test available, boot to that. all tests will be checked except hdd, which will be partly selected. deselect all, and then fully check the hdd test and run. Should run a surface scan. If that hangs or fails that should confirm a bad hdd.

or you can use any of several other surface scanning apps. I use one I made myself.

If you have backups, you're good. Otherwise you need to decide between immediately rescuing your /Users/ data, or just trying to clone the entire hdd. It's been my experience that in ~5% of cases, the hdd checks out, never to return, when trying to do a full disk klone in that condition. (sometimes before even reaching the /Users/ folder) So sometimes going directly after the /Users/ is wise.

Thanks for the advice. But, as noted previously, the iMac is now in the shop, although I probably won't know until next week where the problem lies. My TM backup(s) should suffice if the hard drive requires replacement.

FYI — My 13-year-old iMac (400MHz PowerPC G3), now updated to OS 9.2.2, is chugging right along (ie, working reasonably nicely) after being idle for 2 years. I also updated my browser from Mozilla 1.0.1 to 1.2.1 (the last to run under OS 9), but many websites have been changed so that I can't access them reliably.

UPDATE + QUERIES/CONCERNS

I still haven't heard back from the (Apple-authorized service) shop about my iMac's ills. It's a bad time of year to hit tech services in a university setting.

In the interim a number of concerns occur to me regarding which I'd like some guidance. It's a mid-2011 iMac, Model Z0H6, 2.5GHz Intel Core i5, with 21.5" screen.

(1) Assuming my hard drive is well and truly hosed and requires replacement, I'm planning to have its 500GB Western Digital hard drive replaced with same — I don't need or want greater capacity — unless there's a good reason for me to select something different.
• Would a solid-state drive be advisable (to ward off mechanical failures) or are there significant downsides to such (if indeed it exists for my iMac)?

(2) Assuming that the hard drive is replaced:
• Would not the replacement be a tabula rasa or would it be properly formatted?
• In order to restore my previous set-up via Time Machine, how would that be accomplished if Recovery HD is part of the software on the hard drive (which now has no software)?
• Assuming that somehow Recovery HD is accessible, which does one select to restore everything: the hard drive mechanism (ie, the superordinate drive with ID spec) or the subordinate hard drive with the Mac HD icon (which is user-nameable)?
Pogue's Missing Manual for Lion is ambiguous in that regard, noting under First Aid ~ Repair one thing in one place and another thing in another place.

(3) Is there anything I should be aware/wary of upon return of my iMac? For example:
• If it was opened up in the shop, should I inquire if it was put back together according to original specs (eg, taping), even though it's been looked after by an Apple-certified technician?
• If the drive was replaced, should I obtain written confirmation that the data on the original drive was irrecoverably erased?

LATEST UPDATE:

Tech just got back to me to advise that there are several bad sectors on the hard drive. So the best/cheapest replacement is going to be a Seagate ST1000DM003 1TB BARRACUDA 7200RPM 3.5" 6GB/S to the tune of $90 (+ $75 labor).

Apparently my information from forum discussion 2 years ago regarding reinstallation of software is not as informative as I thought it was: Time Machine can restore my iMac's condition but it can't install the software to make the recovery. So that's going to run another $100+ for the tech to install OS X 10.7.5 (unless somebody out there has a better and immediate solution).
Had I known that, I would have constructed my own recovery partition on a separate hard drive for just that purpose (and once I get the iMac back and functioning again I will do so, after checking via Google or Apple how to generate such). C'est la vie.

I believe your iMac is up to specs to take advantage of "Internet Recovery," but it obviously requires a faster Internet connection than your dial-up.

Edit: OS X: About OS X Recovery

Edit 2: Shame on the tech for either not knowing or not telling.

No, he advised about that. But I have no access to an Ethernet connection.
I have a colleague with both a bootable install disk and external HD, so I should be OK with my restore and recovery.

No access to high-speed Internet either, I assume? (And, by the way, the recovery partition you mentioned in your earlier post requires a high-speed Internet connection to do its thing.)

You might consider backing yourself up with an Apple issue OS X Lion Thumb Drive; they're available on eBay for a reasonable price.

Edit: Y'know, on second thought, maybe you ought to try to beat a thumb drive out of Apple! It's unimaginable that they didn't consider your circumstances as a down-the-road possibility when they stopped shipping install discs and began advising people to bother their friends, relatives, neighbors, and employers, and it would be interesting to see what, if any, plan they've got. (This is the precise situation I anticipated a coupl'a years ago, but it's our first opportunity to plum its depths.)

Go for it!

> I have a colleague with both a bootable install disk.....

Are you certain that the incarnation of OS X on the disc will install on your iMac...that it's not specific to some other Mac?

I made a Recovery Assistant from his Apple-updated system (Lion).
When I get my iMac back (with a 3-year warranteed hard drive), we'll see if it works.

Are you aware that Recovery Assistant requires high-speed Internet?

It's my understanding that it boots into Recovery HD which then permits restore from TM (at least according to the Apple writeup) — plug in drive with RA on it, boot machine via option-R, restore directly via TM.
Am I missing something?

If that's not the case, then I also have access to a bootable OS 10.7 installation DVD.

> Am I missing something?

I guess it's more like I wasn't aware of the option.

Sorry.

Edit: Good luck!

Also, I didn't name it correctly. Here's the blurb from Apple support:

OS X: About Recovery Disk Assistant
The Recovery Disk Assistant lets you create Recovery on an external drive that has all of the same capabilities as the built-in Recovery.
With Recovery Disk Assistant, you can create Recovery on an external drive that has all of the same capabilities as the built-in Recovery: Reinstall OS X, repair the disk using Disk Utility, restore from a Time Machine backup, or browse the web with Safari. This drive can be used in the event you cannot start your computer with the built-in Recovery HD, or you have replaced the hard drive with a new one that does not have Mac OS X installed.
Further info at http://support.apple.com/kb/HT4848 .

PS I wasn't aware of the option either ... until yesterday.

Thanks.

I guess TimeMachine can, indeed, be a useful beast.

(Is Time Machine Apple's justification for its "no disc" policy, even in the face of no high-speed Internet?)

I think Apple's justification for doing away with internal optical drives has several arguments and Time Machine is not part of any of them…

1. The lifespan of complex optical drives such as the SuperDrive is often shorter than the lifespan of the computer and it is a lot easier and cheaper to replace an external drive
2. The lifespan of recorded optical media is not all it was cracked up to be and users are finding CDs and DVDs are unreliabel for long term storage
3. In a time where TeraByte drives are common, the storage capacity of optical discs is ludicrously small
4. As our computing devices get smaller there simply is not room for optical drives
5. The internet is turning out to be the only practical media for sharing data between OS X and iOS devices and the big money is in iOS devices
6. Even though SSD devices are a lot more expensive than a CD/DVD media they are a lot easier to use, not to mention being orders of magnitude faster. I haven't run the numbers but I would venture that when all things are considered using SSD devices is cost coompetitive with optical drives
7. CDs and DVDs are disappearing in the commercial market place and being replaced by downloaded content.
8. With satellite broadband connections there are very few locations where high speed internet is not available. In fact the United states is lagging the industrialized world in the availability of broadband servcie.

I could go on but I think you get the point by now. Optical drives are a trailing edge technology soon to join 8 track tapes as historical footnotes and as always Apple tries to remain on the technological leading edge.

Latest chapter in the saga:

Tech reports that, following installation of new Seagate drive, fans run at higher speed such that the iMac is intolerably noisy. This is likely due to the proprietary firmware in the Apple-commissioned hard drives. (The tech could try out any number of third-party hard drives to see if he could find one that would work properly, but he'd have to charge for the time and effort, with no guarantee that there would be a successful outcome.)

So now the only option is to go to Apple and acquire their officially sanctioned drive (500 GB, SATA, 3.5", 7200 rpm). The major downsides are the cost (3x what the other drive runs), a lousy 90-day warranty (instead of 3 years), and currently a lack of a hard drive in the Apple system (meaning at least a couple weeks' delay in getting my iMac back).

Are we having fun yet?!

Apple's chutzpah is much as it's always been, now coming up on the 30th anniversary of the introduction of the Mac. But what can you do when PCs suck? This is the first major hardware problem I've had with a Mac over 3 decades. So, I guess I've just got to keep a stiff upper lip and bite the bullet.

Nope! (or at least, not likely)

We replace dozens of hard drives a month here. A typical mac has between 7 and 24 temperature sensors in it, most of which are discrete. A few are included in other hardware, such as the die temp on a processor, or the SMART temp reading on a hard drive, or the hard drive temp sensor pins themselves on the back connector.

This allows the mac to zone-control fan speeds, so for example you get more cooling to the optical drive area while burning a disc, without speeding up other fans, or running any fan faster (and louder) than necessary.

In the event that the SMC loses contact with a sensor, gets out-of-range data, or detects some other sensor problems, the sensor is ignored until reboot. During that time, the fan in that zone, or possibly all zones, will be run up to max speed to protect the hardware.

Many hdd manufacturers now include breakout pins on the backs of the desktop sata drives, so the computer can get a direct tap on the temperature of the drive, instead of having to poll SMART or stick a sensor to the enclosure.

Using this connector requires the correct cable, correct wiring, and also the correct baseline information on the kind of reading the sensor is taking. (is that one millivolt per degree, or one microvolt? celsius or farenheight? what's zero degrees?)

When you replace the hard drive with a different model, there's a good chance it uses different baseline information, or a different connector altogether. Some shops will tell you that Apple is doing something "proprietary". They're not, they're just working with Seagate or Western Digital or whoever, according to their specs, and taking advantage of their published product features.

They'll either do this to you out of ignorance of how it works, or that they either don't know how to work around it, or don't want to bother with it.

There are several correct approaches. First is to obtain the correct cable, or modify the existing cable to attach to the new drive. Probe the pins on the different connector and find the correct pair. And hope the baseline information is close enough.

If the pins cannot be correctly matched, or the baseline is too far off, you cannot use the new hdd's temp sensor. The SMC will not be amused when you unplug it. You can sometimes take the OBCC card off the old hdd and sneak it in behind the optical drive and plug it in and keep the SMC happy. Works well with the older imacs.

Or you can try to cobble something up from radio shack, sometimes a discrete transistor junction works fine.

Or you can get online and find some more "universal" temp adapters made expressly for this purpose. They allow you to configure proper baseline info and provide useful temp data without the drive being involved at all.

Finally, you can buy HDD Fan Control, a piece of software designed expressly for this problem. It tells the SMC to ignore the issue. It will also allow you to override fan speeds by directly controlling them in leu of the SMC, to set new low speeds, etc. Handy app. I think it also allows you to feed the hard drive's SMART polling to the SMC instead.

so... don't blame Apple for this one.

Thanks for the info.

I've got to work with what I've got in these here parts. So let it be said, so let it be done. Sadly.

Would it pay to try the same brand HDD as shipped with grelber's iMac, or is the difference more likely to be a proprietary Apple thing that would call for the exact same HDD rather than just the same brand?

Good reply, but it responds to my statement up to the comma, rather than the part afterwards...its crux.

I simply suggested that Time Machine is Apple's backdoor out of grelber's situation, i.e. that not having a high-speed Internet connection does not leave you in a bind with no way out...that unaffordable Internet can be overcome with a low-cost external external HDD loaded with Recovery Assistant and Time Machine backups.

I still say no.

Apple stopped supplying the OS on optical media with OS X 10.7.0. They didn't make Time Machine backups bootable until 10.7.2. If TM were part of the justification, TM backups would have been bootable from the get-go.

I think Apple thought "unavailability of high-speed internet" was a non-issue.

a) Most users have high-speed internet to their home or office.
b) Most of the remaining users have a friend or neighbor with high-speed internet access.
c) In a pinch, you'll visit an Apple Store, or take your computer to a computer repair technician, both of which have high-speed internet access.

In short, Apple probably considers that those complaining they don't have high-speed internet really mean they don't have high-speed internet to their home, which is not actually the same thing.

In the meantime, the benefits of internet-only software delivery are so significant that they greatly out-weigh the "convenience" of having installation DVDs that everyone promptly loses anyway. Nobody ever forgets where they put their internet.

The rare person who really can't get high-speed internet can obtain installers on other media (flash drives, for example). These other media are priced so as to make people consider carefully whether they really truly don't have access to fast internet, or is it just that such access is inconvenient.

The cost equation is: saving millions of users several dollars apiece justifies making a small handful of users have to pay a little more.

Notice that Time Machine is never mentioned anywhere in that evaluation.

I was unaware of the 10.7.0/10.7.2 thing; you're obviously correct about its effect on my argument.

You seem to think that I'm arguing for distribution of install discs with all newly shipped Macs, but I'm not and never have. I fully understand the factors that led to Apple's decision to discontinue discs, and my only argument has been that they were remiss in not having put a program in place to accommodate people like grelber, rather than advising them to be "schnorrers". (As you've read, grelber has no access to high-speed Internet, and tech-installed OS X would have cost him $100; luckily, he was able to schnor a recovery partition, but not everybody in a similar position is that lucky.)

Lion was available on an Apple-produced thumb drive, but Mounty has never been issued in that format, nor, apparently, will Mavericks or any further version of OS X be issued in that format; the "installers on other media" you're touting, with the exception of those Lion drives, are, and will forevermore apparently be, pirated software.

Not exactly schnorring, re Recovery Disk Assistant.

The app is available via Apple ... and has been for a long time. I'm surprised that no one mentioned it when we were having the l o n g drawn-out discussion apropos system reinstallation back in late 2011 — and even more recently via discussion with Apple Care reps. It's a relatively ideal solution as long as one has Time Machine backups; it also obviates the necessity for cloning the drive and eliminates repeatedly cloning to keep things up to date.

There are 2 caveats which accompany RDA's creation and use:
(1) If the computer shipped with OS X Lion or Mountain Lion, the external recovery drive may only be used with the system that created it.
(2) If the system was upgraded to Lion or Mountain Lion purchased from the App Store, the external recovery drive can be used with other similarly-upgraded systems.

Had I known the app existed, I would have created an RDA for myself long ago but been constrained by caveat (1) – no biggie. Since I didn't, my RDA, created as described in caveat (2), can be used on any machine – a fair benefit.

Now all that remains is for me to get my iMac back in functioning condition so that I can find out if the RDA actually works and restores my system via Time Machine to its status at the time of collapse.

And this just occurred to me... It's only a guess, but bootable Time Machine backups seems too momentous to have come in an incremental update, and it's altogether possible that Apple's intentions were that it be included in Lion from the get-go (Edit: It would have made TM a complete package.), but they couldn't get it right until 10.7.2.

Schnorring only in the sense that you weren't aware of the RDA app when you created your Recovery Disk from your colleague's Mac.

I guess the only piece missing from the puzzle is an Apple doc that pulls together all the pieces for people in your situation...lays out all the available options. (Perhaps it exists, but I've never seen a link to it.)

$400+ later and my iMac has returned.

Recovery Disk Assistant employed which then restored my hard drive and recovered my last session on 09-24 from Time Machine. The recovery took 67 minutes (the first 50% took 50 min, the second 50% took only 17 min), but I only had ca 40GB to recover. So far, so good.
The only apparent downside is that backing up after doing all that is taking a honkin' great amount of time.