[Info-vax] ODS-5 data/file recovery

[MG]

On 17-feb-2013 3:56, George Cornelius wrote:
> No, that's not correct.  You want to copy the _unallocated_ blocks as
> well.  Unless you are using erase on delete, you can at least hope that
> the blocks of your file are present there.  It can't hurt to have a
> physical backup in any event.

Firstly, thanks for thinking along with me and all the help, tips
and suggestions.

So, what should I do then?  I don't really understand what you mean
by 'using erase on delete', I'm not deleting or (re)initializing
anything... unless that's not what you mean.


> I assume you mean you found the file name somewhere.  That may
> not mean much - maybe some of the information is in the pagefile,
> for example.  But if you actually did find the individual blocks,
> it is a simple enough matter to create a new file - on a different
> disk since this one's mounted FOREIGN - and copy the blocks there.

It's over ~150 Gbytes or so, it's going to be very painful.  But, I
will naturally try that.  I'm not sure how yet.


> Now if you only found the file name and want to see if somehow
> you are looking at a file header, you can use DUMP on a file
> header block of a known file - a block of INDEXF.SYS - and compare
> to the output of DUMP for the data in question.  You should be
> able to recognize various points of similarity between any two
> header blocks (and there are macros and SDL records defining
> ODS5 header layout).

Sounds like a plan!


> Another idea is to generate another ZIP file that is similar,
> say by number of files present and data contents of the files,
> and try to determine if there is something at the beginning of
> a ZIP file that will ID it.

That is unfortunately not going to be very possible...


> I suppose you will find, at a minimum, the name of the first file
> stored within the archive.  But that's a long road, because you
> will have only come up with a way to recognize the first block of
> the file, and unless the blocks were allocated contiguously, that
> may not help you much with the rest of it unless you really dig
> deep into ZIP file formats and find some way to recognize the
> remaining data (but you could assume it was allocated contiguously
> and just grab a large chunk and copy it to another file and then
> try to UNZIP it).

I will keep it in mind, thanks!

  - MG