Overwritten file, can you get it back?

[FelixTheMacCat]

I never thought I would be a victim of unintentional file deletion, I've always backed my files up in several copies to avoid that.
But here I am.

Ironical enough it happend when i was trying to rearrange my different backups.
I have a 1 TB external usb drive, I back up onto that with time machine.
some time ago I reformatted my macbook and before doing that i created a dmg image of the drive in the lappy.

the reformat went flawlessly and i mounted the dmg and copied across some of the files i need to have with me at all time. I deleted the old timemashine folder thinking all of my files where safe within the dmg.

Last week i ran out of space on my external and i thought, well about time to sort out the last things from the dmg so i can delete that and free the 250gb it occupied.

i tried to retrive my iPhoto library for instance, but i didnt have 50gb of free space on any of my drives so i though, what if i make the dmg file read and writable and instead of deleting the whole thing i could just delete the stuff i didnt need on there.

I opened macintosh HD.dmg with disk utility, selected convert, ticked read and writable and then saved it to the same file, got prompted if i wanted to replace Macintosh HD.dmg with Macintosh HD.dmg, and i thought, hey this might actually work. It didnt, got an error message within second and my original dmg file is now gone. Stupid me.

the space that it occupied is now showing as free space in finder but i havnt written anything to the disk yet. (turned off time machine)

been googeling quite alot on this problem and there is much more help/tips to get on deleted files rather than in my case overwritten files.

Is there any chance to get my dmg back? Ive been trying some data recovery software and it found a bunch of dmgs called D-0001.dmg with acceding numbers, are they related?

Its a 250gb file and it occupied 95% of the space that is now "free" in finder, does that increase my chances of getting it back?

Thanks for reading trough this essay I would be most thankful if you guys could help me,

all the best
Felix

 

[Caleb531]

If you delete a file (e.g. move it to the trash, and empty it), the file can be recoverable. If you overwrite the file, however, it generally is now unrecoverable.

I suppose you could try opening those D-XXXX.dmg files and seeing what's inside.

 

[FelixTheMacCat]

I was expecting that answer.

The answer i was hoping for though was "no worries, its just the file header thats overwritten, the contents is still intact since nothing has been written to the disk. Use this tool to recreate the link to the files contents, good call on unplugging it btw, youre a great guy felix, here, have some money.."

I guess thats not going to happen.

I know some companies do data recovery for a living, could they fix it? What tools would they use in that case?

Its really enjoying cause i know that there in only a few kb or maybe even bytes thats been altered to make my file disappear.

 

[Fishrrman]

Data Rescue might be able to retrieve the dmg file, but not certain.

Suggestion for the future (and I am serious).

FORGET about keeping important files in "disk images".

Keep treasured files in plain "finder format".

DO NOT "encrypt" them, ever.

Get a dedicated "archive drive" that isn't used for anything else except storing this stuff. For even more security, get a SECOND drive and "dupe" the archive to the second drive do that you have an "archive of your archive".

DO NOT use Time Machine, EVER, for archiving important data. Again, you want simple Finder format, copied to an archive drive. Instead, use CarbonCopyCloner or SuperDuper to do your backups and archives. They store in "simple Finder format", easily "seeable" and accessible.

When you make your files "difficult to get at" in ANY way you may find at the most inopportune moment that the ARE "difficult to get at".

For the most important files, accessibility becomes the key.

If the word "security" matters, get a physical SAFE or a safe deposit box at the bank.