Corrupted sparseimage: any hope at all??

[bweylock]

I've been reading everything I can find here, and my problem does not seem to have occurred to anyone else. Either that, or maybe it's so bad that most people have better sense than to ask for help.

I have a large (>50GB) encrypted sparseimage file that was recommended to me as the best way to encrypt data on a drive. It is on an external FW400.

While writing to and reading from it yesterday, there was a power failure.

Now it will no longer mount. The error message is "corrupt image."

Disk Utility will not verify it, nor will hduitil verify.

The only suggestion that seems to apply to this case is to run a terminal script to convert it from a sparseimage to a dmg and then use filejuicer to see if I can get some of my video and jpeg files out. Does that make sense?

If so, could someone give me the syntax for myDrive/myFile.sparseimage? I can't figure out where to plug my information into the suggested terminal command line.

Anything else to try? Can't use DiskWarrior or Data Rescue because it won't mount and be recognized as a volume.

Thanks!


Best,


- Bill

10.4.1, 1.5 GB RAM

[yellow]

If so, could someone give me the syntax for myDrive/myFile.sparseimage? I can't figure out where to plug my information into the suggested terminal command line.

What command was suggested?

[bweylock]

Doesn't matter anymore.

Nothing works on a corrupted disk image file.

This is something that should be posted VERY clearly whenever someone is advised to use these @#$%! things.

One little flash of power, and 50GB of data is lost forever?

Would we call that a good medium to work in?

And if one more person tells me I should establish a backup policy, I'll scream so you can hear it through the italics.

I do back up data, but I don't do it more than once a day. That allowed me to lose only about 4 GB of new and revised files.

Yes there are limits to my pain, but that's a lot of data.

Anyway, thanks for responding.

To be more polite than colorful (changing gears to do that), it was a command syntax for hdiutil convert xxx.sparseimage to xxx.dmg. Without bothering to look it up it involved -o and -format.

Tx.

[Norm Nager]

Bill, sorry you experienced the power failure and the corruption of the sparse image you were copying.

After learning a lesson the hard way, I went out and bought an APC UPS battery backup system, a model that takes over not only during a power failure but also during brownouts or other voltage feed problems.

I keep my Mac, monitor, keyboard and external FW drive plugged into it.

Respectfully, Norm

[Mr_V]

I've just encountered the same problem - an encrypted sparseimage became corrupted after I was forced to hard-reset my PowerBook when OS X became unresponsive (something that's fortunately rather rare).

In my case it's only 500MB of data that I can regenerate, so I'm not quite about to jump off a bridge, but... I would obviously prefer not to have to spend the time doing that.

So, is the answer to this issue still that there is no answer? Just checking...

[bramley]

So, is the answer to this issue still that there is no answer? Just checking...
The reason for corruption of files that are being written to when powerloss occurs is mostly because the file is left in an incomplete state. Hard drives work more slower than CPUs and read/write operations must be buffered i.e cached in memory. Powerloss means this data is lost and the file on disc is corrupted (incomplete.)

Solving corruption of this sort is hard, and in the special case of encrypted disc images virtually impossible. It will always be so. The only protection is a good backup.

Note that data corruption of files not being read or written to during powerloss may occur because the hard drive head hit the HDD's surface where your file is stored, or caused a change in the magnetic properties of the HDD's material at the same location. The corruption is not necessarily the fault of the powerloss, but may have some other cause. i.e you only noticed it after the powerloss - there's not necessarily a connection.

In any case repairing the drive (not repairing permissions!) should be carried out in the manner described in Disc Utility's help.