NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/sys/amiga/hardware-part1/5863

Text File | 1996-08-05 | 3.7 KB | 74 lines

Newsgroups: comp.sys.amiga.hardware
Path: netnews.upenn.edu!dsinc!scala!news
From: [e-mail] (Dave Haynie)
Subject: Re: DiskSalv4?????
Sender: [e-mail] (Usenet administrator)
Message-ID: <[e-mail]>
Date: Thu, 29 Feb 1996 21:26:08 GMT
Reply-To: [e-mail] (Dave Haynie)
References: <[e-mail]> <[e-mail]> <4h1qmf$[e-mail]>
Nntp-Posting-Host: gator
Organization: Scala Computer Television, US Research Center

In <4h1qmf$[e-mail]>, [e-mail] (Douglas Rudd) writes:
>Mark Harden <[e-mail]> writes:
>
>>DiskSalv4 was commissioned by Fourth Level Developments to include support
>>for Ami-File-Safe (AFS).  If you don't have AFS you don't need V4.  If you do
>>you can upgrade for 25 UKP.

>>E-Mail [e-mail] for details.  Note that currently V4 only supports
>>SALVAGE mode for AFS partitions.

>And this it does less than perfect. In my case, DS4 misses several sub-
>directories, re-names the files to match names of other files, but with
>different content. In short, the results are a real mess.

Things will improve a little in the next release (a free upgrade, of
course), but the extent to which this is possible is very
limited. When you delete something in AFS, it's gone, gone,
gone. Well, almost (obviously, if it were totally gone, DiskSalv
couldn't do anything). AFS keeps a short list of the last few items
deleted; this was added too late for the current release, but it'll be
supported in the next release. The other thing DiskSalv can do is find
older copies of a directory entry for the thing you're after. When you
update a directory, AFS makes a new copy of that block before
unlinking the old one -- a runtime security issue, of course. Some of
these blocks may hang out for awhile, they're not explicitly deleted,
but they do get reallocated. At present, DiskSalv sorts through them
and tries to give you the thing you're after, though it could well be
that the old pointer DiskSalv has found references something else. And
there can be any number of these old pointers, pointing to any number
of disk locations. In the future, you'll be able to see multiple
references in the DiskSalv browser if they exist on-disk.

>There is a LOT of stuff on that drive and I still can't get it all
>back.

After the deletion record (20-30 items, as I recall), you may very
well lose everything else after a delete. DiskSalv works well under
FFS because you can delete every single file and directory under FFS
and still find them later, thanks to FFS's distributed directory
structure (the reason FFS directories aren't especially fast). AFS
uses a packed directory structure that's kept separate from the data
blocks, and when you delete something from a directory, you're
deleting the point to that object, not just a link as in FFS.

There will be some additional help in the future release, too. AFS
uses indirection nodes (ANodes) to track disk storage. The directory
headers reference things in ANode space, not disk block space. So even
if a directory entry is gone for good, DiskSalv may be able to find
what you're looking for by harvesting any unallocated ANode chains
that may still be around. There's no way of telling the proper name
for such things or where they belong in the disk hierarchy, but it is
possible to retrieve intact files this way. And lots of garbage, since
the content blocks could have been reassigned (but likely haven't been
immediately after you delete stuff).

Dave Haynie          | ex-Commodore Engineering |   for DiskSalv 3 &
Sr. Systems Engineer |  Hardwired Media Company | "The Deathbed Vigil"
Scala Inc., US R&D   |    Ki No Kawa Aikido     |     [e-mail]

         "Feeling ... Pretty ... Psyched" -R.E.M.