._dd file extension

[Jessica Venlet]

Hello,

I'm working on an accession of files from 3.5in floppies and have noticed several files with this extension: ._DD. Droid was unable to identify the file format. I opened a couple files in a text editor and Quick View Plus and between jumbled characters there seems to be some information worth preserving. A google search on this extension led me to some information (linked below). The files might be related to Norton Disk Doctor software that was used to recover files from a hard drive.

Has anyone encountered files like this before? Did you find any strategies that helped to make the files more usable? 

Thanks in advance,

Jessica Venlet

UNC Chapel Hill University Archives 

._dd resources:

• http://www.solvusoft.com/en/file-extensions/file-extension-_dd/
  
• http://dotwhat.net/file/extension/_dd/6092
  
• http://www.brighthub.com/computing/smb-security/articles/104771.aspx
  
• maybe relevant? https://en.wikipedia.org/wiki/DiskDoubler

[Michael Kjörling]

On 18 Jan 2017 10:58 -0800, from jmve...@gmail.com (Jessica Venlet):

> I'm working on an accession of files from 3.5in floppies and have noticed
> several files with this extension: ._DD. Droid was unable to identify the
> file format. I opened a couple files in a text editor and Quick View Plus
> and between jumbled characters there seems to be some information worth
> preserving. A google search on this extension led me to some information
> (linked below). The files might be related to Norton Disk Doctor software
> that was used to recover files from a hard drive.

If those are DiskDoctor recovered files, then the contents could for
all intents and purposes be anything. (In that case, ._DD files would
be similar to those that e.g. CHKDSK would spit out as FILE????.CHK.)
Knowing FAT's reliability (I assume this is from FAT-formatted
floppies), or rather lack thereof, they could equally well be
fragments of files resulting from either file system damage or buggy
file system handling code. It's possible that the files even contain
only _fragments_ from larger files, which may be why you are having
trouble identifying the actual file format.

I would suggest checking other files on the same media to see if they
have what appears to be "gaps" (which may show up as all empty
regions, or regions filled with random-looking data) in similarly
structured data, where the ._DD files could conceivably fit within
those gaps. If you find any, focus on identifying the format of those
larger files, as it is likely that they are related.

--
Michael Kjörling • https://michael.kjorling.se • mic...@kjorling.se
“People who think they know everything really annoy
those of us who know we don’t.” (Bjarne Stroustrup)

[Creighton Barrett]

Jessica, did you find anything that worked with these files?

I just ran into some ._DD files, also found on 3.5 inch floppies (FAT12). I also thought they were DiskDoctor recovered files, but then I saw Michael's response to your question. In this case, I now feel like there may be something wrong with the file system. Where I usually see NONAME [FAT12] in the file path, I now see:

/┼▀Ü/π8Z(Ü.π [FAT12]/[root]/FILE0003._DD

Some of them seem to be fragments of files, but others seem to be complete files. In one disk, there are 206 files, 177 of which are ._DD files. I can find content relationships between some of the ._DD files and the other files, but in most cases the other files are missing an extension.

Anyone else come across this before?

Thanks,
Creighton