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Things to do in Denver when your Hard Drive is Dead
January 31, 2011 8:18 AM   Subscribe

What would cause a 320Gb hard drive to report as 2.2Tb?

I am attempting to recover files from a friend's HD. It is a 320 Gb WD Caviar but is reporting as 2.2Tb. It was originally formatted with HFS+ but now none of the utilities I've tried (FileSalvage, Data Rescue, R-Studio, Drive Genius) can find any directory info and the transfer rate is so slow that a deep scan will take about 100 days.

I'm on the verge of telling my friends to take it to a professional data recovery facility who can physically rebuild the drive if necessary (10 years worth of photos, don't ask) but would appreciate insight as to what kind of a problem this is. The drive is quiet and not making any horrible sounds right now during reads.

The actual read speed reported by utilities is in the 12-14 mb/s range over USB 2.0.
posted by unSane to Computers & Internet (9 answers total) 2 users marked this as a favorite
 
did he have a RAID?
is the jumper in the correct position...

similar problem here: http://forums.buffalotech.com/t5/Storage/Dropped-external-hard-drive-while-operating-is-there-any-hope-at/m-p/36051
posted by fozzie33 at 8:25 AM on January 31, 2011


no RAID, was in an external USB enclosure

I've looked into the jumper thing but can't find any further info on that, suspect it may be an urban myth

it would help just to know HOW exactly a drive determines its own size when it reports it to the host
posted by unSane at 8:34 AM on January 31, 2011


Strange, my hard drive is doing the -exact- same thing. It's a Seagate Momentus 5400.5 320GB HD that was in one of those Seagate FreeAgent enclosures. No strange noises but when I can actually get it to read (not all SATA -> USB things work and I haven't done the SATA -> IDE thing yet) it shows up as a 2TB drive.

It's even an HFS+ drive, too.

I'll let you know if I make any progress.
posted by Loto at 8:45 AM on January 31, 2011


A jumper isn't going to make a drive appear to be larger than it really is. But there are jumpers on some drives that will tell it to appear as SMALLER than it really is, so older equipment can use it.

Your problem sounds like the MBR (containing the partition table) (or whatever HFS+) uses has gotten corrupted. That's how the computer sees how large a volume/partition/drive letter is. The part table says "this drive has 400,000,000 blocks of 512 bytes, and partition one goes from block 1 to block 12,345,678" If that gets messed up, the computer thinks it is the wrong size. Note, it isn't necessarily a bad thing if it reports as too big, if you are just trying to read from the drive. But it isn't a good sign either.

(It is possible, though not likely, that the enclosure it was in was doing some translation that the connector you are currently using doesn't understand. I have seen where drives that came out of weird enclosures or older computers just didn't get recognized by some drive-to-usb connectors. Hooking it directly to a computer via IDE or Sata would be better.)

Or the electronics on the drive are messed up and reporting a much larger size to the computer.

Are you trying to recover the data on a Windows machine? That may be part of your problem. I don't think it understands HFS+ at all, and I doubt many non-Mac-specific file utilities will understand it either.

What actually happened to the drive that made it unreadable on the Mac?
posted by gjc at 8:58 AM on January 31, 2011



it would help just to know HOW exactly a drive determines its own size when it reports it to the host


The drive doesn't report its size, really. It just reports what parameters it has available. The computer then builds a partition based on that. In your case, the drive is having trouble reading data for some reason. Partition information is data, and so the drive is reporting incorrectly.

The jumper thing is because there are a couple different ways that drives can communicate to controllers what the drive can do, and setting a jumper allows the user to choose. Make the wrong choice and wacky behavior results. Not all drives have them.

As for what the specific problem is - I can't say because I don't have enough information. Your experience so far is typical of what a drive recovery will be like.

In my experience HFS+ is fairly notorious for this, and some of the newer file systems are better for external drives and make recovery easier. However, support for newer file systems is iffy in OSX, so... yeah. Anyway, the lesson is, don't put precious things on external hard drives. That is just asking for trouble.

A recovery program is going to have to go block by block, try to figure out what is there and what is relevant and what is not and piece the file system back together. As you've found, it's a very tedious process. And it's not guaranteed to work because if the drive were reliable it wouldn't have failed in the first place.
posted by Pogo_Fuzzybutt at 9:12 AM on January 31, 2011


The last time I had a drive with a weirdly, abominably slow transfer rate, I tried ddrescue, and it worked great! It does a bit-for-bit copy, filesystem agnostic. I would experiment with it if I were you. It requires some sort of Unix flavor to run (such as a Mac, using DarwinPorts); it is included in the System Rescue Linux boot package. Here is an askme search for ddrescue.
posted by thejoshu at 10:24 AM on January 31, 2011


I am not sure if this helps, but 2.2TB is the maximum partition size that many BIOSes and OSes can handle:
http://www.uefi.org/learning_center/UEFI_MBR_Limits_v2.pdf
posted by dhens at 11:10 AM on January 31, 2011


I don't see Alsoft DiskWarrior in the list of programs you've tried. It can often work "miracles" where other programs fail. I'm not familiar with the specific symptoms you're seeing, but it's worth a try -- definitely cheaper than sending the drive to a recovery place.
posted by SomePerlGeek at 2:58 PM on January 31, 2011


Disk Warrior doesn't work because the disk won't mount, sadly.

At this point I don't see any other solution than having the disk sent to a place that can physically replace the logic board and see if that works. I would clone it block by block but the access times are so slow it is impractical (would take weeks).
posted by unSane at 4:42 PM on January 31, 2011


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