How can I troubleshoot an external drive that won't mount?

December 3, 2007 6:36 PM

External firewire drive was working fine with Mac laptop, now won't mount. I hear it make its usual startup noises and then I feel it spinning happily, but the OS can't see it. I've tried lots of troubleshooting steps (list inside); can you think of others I should try?

I'm running Mac OS 10.4.10 on a MacBook Pro. This is a 2.5" drive inside a MacAlly firewire enclosure. This setup has worked perfectly for a year.

- Drive and enclosure were both bought new a year ago and have led an easy life (pretty low usage, no physical impact/trauma).
- No magnets near the drive.
- No other hardware issues with the laptop (ever).
- No power events, I assume -- there hasn't been a storm, my building's power is modern, the laptop is plugged into a surge protector (enclosure draws its power from the firewire port).
- No changes to the OS or to any software in between when it mounted and didn't.
- Drive is spinning silently, no clicks or other noises. Vibration of spinning feels the same to me as always.
- Indicator LED on enclosure is lit up as usual when drive is powered on.


I've tried, with no success:
- restarting Mac (several times).
- connecting drive with its on/off switch already turned to on (usually I'd connect it with the switch off, then turn switch to on).
- relaunching Finder while drive is connected & spinning.
- opening Disk Utility, in case OS is seeing drive and just not displaying it in the Finder (no luck -- only drive displayed in Disk Utility is my internal HD).
- trying to mount it connected by USB rather than Firewire (enclosure has both full-size fw and mini usb connections). This might not be a useful test since I've never tried mounting it by USB in the past, so I don't know if it can draw enough power from the USB port (and I can't find the little AC cable it came with for situations when it can't draw enough).


I don't have another 2.5" enclosure on hand, I don't have any other device that connects via Firewire, and it will be a week until I have access to another person's Mac to test it that way.

Please let me know any more troubleshooting I can do with just my own laptop, the drive & enclosure, and Firewire & USB cables. Thank you!

posted by sparrows to computers & internet (9 comments total)

If you can get access to Disk Warrior, that would definitely be my next step. I have a problem drive that freqently gets hosed up and only DW can get it to mount. Then it is fine for a while.
posted by mzurer at 6:44 PM on December 3, 2007

What does System profiler say under FireWire? (apple menu -> about this mac, then click on 'more info...') Do you see the firewire device? a drive?

Howabout if you connect via USB?

Might be a bad firewire/usb bridge. If so you can get a new enclosure and get the data off of the drive.
posted by cftarnas at 6:51 PM on December 3, 2007

How long is the cable you're using to bus-power the drive?

I've had problems with my Macbook Pro and my bus-powered external 2.5" enclosures where if I use a Firewire or USB cable longer than 6 feet, the drive either doesnt fire up, or if powers up, but OSX has trouble seeing it (and randomly dismounts it if it does). Shorter cable runs are recommended if you're not using a dedicated power supply.

another odd thing I discovered recently that may or may not apply to you (since you mentioned Firewire instead of USB), but I determined that my 2.16 Ghz Core Duo Macbook Pro will flat out refuse to bus-power any device that's plugged in to the USB ports on the left side of the laptop. But when you connect the cable to the right side ports, everything works great.
posted by melorama at 7:19 PM on December 3, 2007

Not enough power from the FireWire to run the drive reliably? This just happened to me with a 2.5" USB drive and MacBook Pro Can you plug a power adaptor into the drive? Try plugging it into a desktop machine and see if it works better.
posted by Etaoin Shrdlu at 7:24 PM on December 3, 2007

I agree with the suggestions to plug in dedicated power. The only other thing I would suggest is to go to the Apple menu, choose About this Mac, click the More Info button, and then inspect the FireWire section to make sure the bus is still recognized. I have an occasional problem with the FW bus on my G5 that requires me to reset a chip on the logic board.
posted by pmbuko at 7:36 PM on December 3, 2007

It sounds like the data portion of your Firewire cable has gone bad. Or your Firewire port.

Bus-power USB is heavily dependent on several factors I wouldn't trust to a simple "plug it in and see if it USB powers". There are cables with two USB connectors on them which will power an external drive fine.

See if you can scare up another 6pin-6pin firewire cable. If that fails, see if you can scare up a FW800-6pin firewire 400 cable. They exist, just not terribly common.

After that, try a different enclosure.

Then, it's at the drive.
posted by tomierna at 8:46 PM on December 3, 2007

Thanks. I've tried with two different fw-400 cables, one that's 12 inches long and one that's 36 inches long.

This drive has mounted fine using the 36-inch cable for more than a year, with no external AC, so I'd be surprised if power is the issue -- it's hard to imagine what would change to make power suddenly be the issue.

The drive is not listed, when connected either with fw or USB, in System Profiler (nor is it listed, as I said, in Disk Utility).

System Profiler does still list the fw bus.

I will try to get access to a copy of Disk Warrior...
posted by sparrows at 11:33 PM on December 3, 2007

Check with the drive manuf , and see what they they consider a sufficient test for failure on your system - If it fails that, not only is it almost certainly a drive problem, you've got a leg up on a possible warranty claim.

Dumb question - Have you considered just putting the drive in your pocket, and walking up to a machine at a retailer and plugging it in to see if it works? Likewise, you might want to consider purchasing another drive/enclosure to swap parts around with until you have something working, and just keep the spare {drive, case, bits} to use in case there's problems in the future.

Seconding everybody noting that USB powering a drive is iffy at best, and that you might want to do a browse around the house for a similar wallwart (same volts, mA and plug) in use by something else , in order to try it out.
posted by Orb2069 at 9:59 AM on December 4, 2007

Let's forget about USB, I only mentioned it as another thing I tested.

This drive has been successfully used all its life as a *Firewire* drive, with no external AC.

I don't have time to get to Apple Store (and other stores don't have Macs out for retail), but that's a good idea for when I do have time, thanks.
posted by sparrows at 12:04 PM on December 4, 2007