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[OM] Re: File recovery

Subject: [OM] Re: File recovery
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Sun, 08 May 2005 09:24:09 -0400

Joel Wilcox wrote:

> The Lexar recovery software did a great job.  Got everything back and 
> anything else that hadn't been written over in the meantime.
> 
> At 06:26 PM 5/7/2005 -0400, you wrote:
> 
>>First, I would advise you in the future to never have your computer
>>write back to the CF card.  Supposedly it's logically a standard FAT or
>>FAT-32 disk but I've heard too many stories of incompatibilty with the
>>camera.  Perhaps it's nothing but the directory structure that the
>>camera expects but I prefer to stay away.
> 
> 
> 
> I think I'll stay away henceforth as well.
> 
> But, yes, it sounds like you haven't tried it, 

This is very true.  I don't have any Olympus digital gear or software.

and in fact it has never
> been a problem to write to the CF card, and that certainly wasn't the issue 
> in this case (unless attempting to delete is a form of writing -- not being 
> a smart aleck, since I think deleting is really writing a filename 
> change?).

When it works as it's supposed to it's only a single bit that gets 
changed.  The bit indicates that the file has been deleted and that any 
space occupied by the file is available for re-use (if needed).  The 
space will not actually be re-used unless there is no other free space 
available.  This is precisely to allow for recovery of accidentally 
deleted files.  To show my age, I was actually there when this design 
change was made to PC-DOS about 20 years ago.  Your camera runs a DOS clone.

Although it's only a single bit that is supposed to change it's not 
possible to read or write anything other than "clusters".  A cluster is 
a group of 1 or more "sectors" which are blocks of 512 bytes.  So, 
changing a single bit means reading and writing a minimum of 512 bytes 
and possibly much more depending on CF size.  If the Oly software has a 
bug (what software doesn't) it gives it an opportunity to corrupt 
something else in that block of data.  I believe in not offering the 
opportunity if it can be helped.

   But if this is bad practice, I blame Ag Schozz entirely, since
> he put me on to the practice of doing all sorts of things in Viewer prior 
> to transfer to the hard disk -- no doubt to punish me for getting my OM 
> adapter before he did.  My revenge will be calculated and subtle. >:^P
> 
> (OK, just kidding, Ken.)
> 
> 
>>All that said, it would appear that you've located a bug in Olympus
>>Viewer.  Hard to say what it actually did except that it wrote some
>>trash to the CF card somewhere.  I think it's highly unlikey that it
>>actually erased all the images, however.
> 
> 
> All's well that ends well.  First time through the software located all my 
> .jpgs.  I had to go to preferences and change them to get it to find my 
> ORFs during a second pass.

I was pretty well convinced that you hadn't actually lost more than a 
single file if anything at all.  Glad it all worked out and that you 
were able to use it.  Since the version 2 software was labeled an 
upgrade I thought you might have to have version 1.5 already installed 
and version 1.5 was not on the web site.

> 
> Thanks again, Chuck.
> 
> Joel W.
> 
> 
> 
> 
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