Internal HDD mounting problem (OS X)

Specs: Mac Pro, running OS X 10.6.6. 9 GB RAM. One 1TB HD (boot drive), 3x1.5TB HD, all internal bays. I use the computer for heavy photo editing, ftp, and general web surfing.
It is about 2 1/2 years old. The boot disk has about 100 GB of free space; two of the 1.5 TB drives are 95% full. The last one has about 800 GB of free space on it.

Today, I restarted my computer after some general slowness. I noticed a Console message regarding some problem with VM or a swap file. Unfortunately, I don’t remember the exact message, and I’m not at my desktop at the moment. Upon reboot, I noticed one of my full hard drives (simply named Internal Bay 2) no longer appeared on my desktop. Odd. I go into Disk Utility, and it’s there, but greyed out. S.M.A.R.T. status is verified, and says the drive is OK. I try mounting it, and Disk Utility hangs.

I run Disk Warrior, and Disk Warrior also sees it, no problem. I fix the directory, it shows me all the folders on the disk after the verification process, so all my data seems to be there. However, it, too, doesn’t remount the drive (I’m not sure if Disk Warrior normally mounts unmounted drives or not after completion of the directory optimization.) So I reboot the computer. Still no drive.

I shut down the computer, and it hangs on the blue screen at the shutdown, with that spinning little icon (not a beachball, but the startup and shutdown icon–like the one that appears below the Apple logo as you’re starting up the system.) I wait about two minutes, grow impatient, and force a shutdown by holding down the power. I remove and reinsert the drive. No dice. Shutdown. Same weirdness, had to force it.

I remove the harddrive, stick it in an enclosure, and connect it to my MacBook Pro. It’s fine–it shows up, data is there and accessible. (The disk is backed up, anyway.)

I haven’t done any general maintenance on the boot drive, and Disk Warrior says that 34% of the directory is out of order, so I rebuilt the directory, and am currently running a file system check on the boot drive. After removing the hard drive, the desktop didn’t seem to have any problems restarting (although I only tried “restart” and not “shut down”–I’m not sure if the two routines are significantly different.)

My next step is to stick another hard drive in the empty slot and see what happens. I’m not going to be able to get around to that until tomorrow.

In the meanwhile, how concerned should I be (like I said, my data is backed up), and what should I be looking out for? Does this sort of behavior sound familiar to anyone? First, I get that odd paging file log entry, then the drive won’t mount internally (even though it’s recognized by Disk Utility and shows up fine in a hard drive enclosure), and then the computer won’t shut down properly. I did notice today that the computer seemed to be running slower than usual. Is this just a run-of-the-mill drive issue, or could it be something more serious?

Can’t say I’ve ever seen anything like that, but my guess would be a hard drive on the way out. If you know how to use Darwin Ports, smartmontools may give you a little more info on what the drive’s been through.

Do you happen to know the file system for this drive? The “default” is HFS+ (Journaled), which Disk Utility calls “MacOS Extended (Journaled)”.

Pretty sure it’s HFS+ (I can’t see why I would have formatted it as anything else). I’ll check when I get home.

Try an remove and re-insert on the drive in bay 1 (i.e. the drive that mounts just BEFORE the one you’re having trouble with). When I had a “loose” (not entirely inserted into the backplane connector) drive a while back, one symptom was to cause the drive after it on the backplane not to mount intermittently. But generally, I’d agree the disk is on it’s way out: I think the mount will be skipped if an internal drive doesn’t respond in a reasonable amount of time; that timeout’s almost certainly longer when the drive is connected externally.

Possibly stupid question: If the drive is unmounted, is it hot swappable, or do I need to shutdown? I’ve always turned off the computer to avoid the problem, but I don’t know whether this technically necessary.

Second question: So what could be going on that the drive is visible to the system via Disk Utility and Disk Warrior but not mountable, and such that Disk Warrior can actually organize the directory and tell me what’s on the drive? I guess this question is more of a “how do does drive mounting work” that helps me better understand how my computer sees things and helps me diagnose problems better in the future. Related to that question, how does the shutdown hang fit into this? I assume the computer is trying to do something with that drive as it shuts down and it just causes the system to stall?

Third: Is there anything I should be doing to check the health of my drives intermittently, other than relying on the S.M.A.R.T. status, which always seems to be OK, even on drives for me that have failed in the past? Or is it really just one of those things that, usually, when it goes, it goes.

Having had vaguely similar problems on a pc ( running OpenSUSE ) with a 1.5TB SATA disk winking in and out and losing stuff and fscking it every other day, I eventually decided it was not the disk, nor the rather flimsy SATA cables which I was changing over frequently — as there could be a fault from the bending of the cable or the connectors being loose — but the SATA controller on the motherboard ( it is ASUS ). And so something that was not worth fixing.

The disk works perfectly in a USB extension dock. I can play video directly from that disk woth no degradation.
I could have easily been led to the idea my drive was dying, or that the OS was to blame.
[ I don’t know if Macs allow USB extension drive docks. ]

Well, I threw in another drive into the second bay, and it mounted fine. I guess I’ll just retire the (apparently) failing drive. None of my disk utilities indicate there’s anything wrong with it. Checks out fine with Disk Warrior. fdsk_hfs isn’t showing any weirdness.

Interestingly enough, I download SMART Utility for my MacBook Pro (forgetting that it won’t work on externally mounted devices), and I got a warning that on this computer, my hard drive is failing, even though Disk Utility shows its S.M.A.R.T. status as “OK.” Ugh. Two hard drives now?
I haven’t noticed any issues at all on this computer, though.

Huh. I was able to remount the internal drive on the MacPro, and able to run that SMART Utility on it. No bad sectors, no errors, no nothing.