Help me save a troubled external hard drive!
November 29, 2011 1:03 PM   Subscribe

Help me save a troubled external hard drive! I'm using OSX and I'm fine with wiping it out and starting over. This may be complicated?

I'm one of those crazy people who back up everything. And, as luck would have it, the troubled hard drive is my backup HD, so there's nothing on it I need to save. The drive in question is only 2 years old. It's a Seagate Free Agent something or other USB drive.

Problem: I can't reformat it in Disk Utility. In the First Aid tab, doing a Repair Disk shows that the disk is fine. But if I try to erase the disk, Disk Utility gives me an error, saying "Couldn't Unmount Disk"

I even tried restarting from the Lion recovery partition (or whatever the heck that's called) and using Disk Utility there. No luck.

All I want to do is erase the HD and zero out all data so the drive will check to make sure everything works and cancel out any bad sectors, and then I want to partition this huge drive into 4, to match the 3 drives I'm backing up plus a scratch drive.


If I absolutely have to for some odd reason, I can use a Windows XP netbook to help this process, but I never use that thing, so I have no experience with XP nor software other than XP itself.
posted by 2oh1 to Computers & Internet (23 answers total)
Just to be clear - I know how to do everything once I can get the drive reformatted. But since OSX isn't able to mount and then unmount the disk for Disk Utility, I'm stuck.
posted by 2oh1 at 1:05 PM on November 29, 2011

Are you running Time Machine or other software that is using the disk while you're also trying to reformat it? Turn that off and quit any applications that are running. You could also try a utility like What's Keeping Me? to get more specific process info on on any background processes (virus scanner? DropBox?) that might be using the drive.

(If you have any further weirdness I would advise scrapping the drive and buying a new one. You don't want to run into other problems when you actually try to restore a backup.)
posted by bcwinters at 1:09 PM on November 29, 2011 [1 favorite]

A friend of mine recently had the same issue unmounting an external HD, with the same "Couldn't Unmount Disk" error. He ended up formatting it using a Windows laptop.
posted by Utilitaritron at 1:13 PM on November 29, 2011

Disk Warrior. I've had some fucked up drives, and it's never failed me, ever.
posted by nevercalm at 1:44 PM on November 29, 2011

to be fair

portable (platter) hard drives crapping out after two years is far from uncommon, especially if you've been carrying it around in your backpack or somesuch
posted by Oktober at 1:57 PM on November 29, 2011

The drive has sat on a shelf. Used nightly for backups, but otherwise never touched or moved. I'm 99% sure that all I need to do is reformat it. The question is how?
posted by 2oh1 at 2:18 PM on November 29, 2011

Wow. I really thought someone would come along and say "Here's how to do this on XP." I'm starting to suspect I'll have to do that (or buy Disk Warrior for $100. I know Disk Warrior would work. I used it a decade ago on what I assumed was a dead internal drive. Disk Warrior fixed it quickly... but I'm not going to spend $100 for one use on this drive).
posted by 2oh1 at 2:27 PM on November 29, 2011

Welp, in XP it's just run->cmd , then at the command prompt, "format driveletter:"
posted by Oktober at 3:18 PM on November 29, 2011

where, uh, driveletter is whatever letter is assigned to the drive
posted by Oktober at 3:20 PM on November 29, 2011

I don't know anything about XP. I only use the laptop for testing web design in IE, so I have no clue about drive letters or even what run->cmd means. Run in what? An app?
posted by 2oh1 at 3:24 PM on November 29, 2011

Have you tried re-partitioning it first, before formatting?

I've seen the same issue on my Mac, mainly on NTFS-formatted drives (though that might be a furphy - I suspect it's down to my gf not waiting until things finish unmounting properly in Windows on a drive we share between our 2 laptops & the TV). It won't allow me to re-format it, but it will allow me to re-partition it. Once that's done, it formats fine.
posted by Pinback at 3:31 PM on November 29, 2011

Thanks for the idea Pinback. I just tried that, but I got the following error: "Unable to write to the last block of the device."

I really need to figure out how to reformat it in XP. Every google search I've done has led to that answer, but nobody explains how to do it, or they say things that only make sense to an XP user.
posted by 2oh1 at 4:04 PM on November 29, 2011

In XP, go to "Control Panel". open "administrative tools" then "Computer managment"

Under "Storage" should be a panel called "Disk Management".

From here, you can repartition and format the drive - assuming of course that the drive will let you.
posted by Pogo_Fuzzybutt at 4:12 PM on November 29, 2011

I did what you said Pogo. I'm in Disk Management and I see the drive, but I can't figure out how to format it.
posted by 2oh1 at 5:03 PM on November 29, 2011

This is crazy. XP sees the drive and says "Healthy (GPT Protective Partition) but the option to format it is grayed out in the Action > All Tasks menu. Everything in that menu is grayed out.
posted by 2oh1 at 5:11 PM on November 29, 2011

Disk Management is the complicated way to do it. If the drive shows up in My Computer, just right-click it there and pick "Format". You probably want to pick "Quick format" in Windows if you plan on formatting it again on Mac.

I don't have XP available to check, but in Disk Management I'm pretty sure you can just right-click the volume (the graphic showing your paritions) and pick Format. Alternatively you could delete the partition entirely and re-create it (all of this is in right-click menu).
posted by neckro23 at 5:12 PM on November 29, 2011

I don't see the drive under My Computer, but it's not like I'd know where to look. I assume "Removable Disk E" is the SD card reader (though it has no card in it). The only disk listed is Local Disk (C:) ...should this HD be assigned a letter?
posted by 2oh1 at 5:20 PM on November 29, 2011

Hmmm... XP Probably can't use the drive because it's formatted for a Mac. But why isn't XP giving me the option to format it?
posted by 2oh1 at 5:24 PM on November 29, 2011

If the drive is either unpartitioned or formatted in a way windows doesn't understand, it will only show up in Disk Management.

Which is to say windows only assigns drive letters to mountable partitions.

You need to partition the drive for XP before you can format it. If it was used on a mac then it was probably using a GUID instead of MBR and so you need to use disk management to put an MBR on it so XP knows what to do with it.
posted by Pogo_Fuzzybutt at 5:47 PM on November 29, 2011

To put an MBR? What's an MBR and how do I do this?
posted by 2oh1 at 6:01 PM on November 29, 2011

Ah, master boot record. Under Properties, it says Partition Style: Master Boot Record (MBR)
posted by 2oh1 at 6:03 PM on November 29, 2011

"Removable Disk E" is probably your hard drive. By default I'm pretty sure XP hides card readers unless there's a card in there.
posted by neckro23 at 6:04 PM on November 29, 2011

I knew this would be super simple to solve, and it was. I'm actually shocked nobody here recommended this: The solution was to create an Ubuntu live CD (on an SD card, actually) and use that on my Netbook. Ubuntu had no trouble seeing the external hard drive and formatting it. I then plugged the drive into my Mac and reformatted it without any trouble at all.

Problem solved.
posted by 2oh1 at 12:34 PM on December 1, 2011

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