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Re: undeletion at filesystem level or in extra filesystem?

From: Thomas Bushnell, BSG
Subject: Re: undeletion at filesystem level or in extra filesystem?
Date: 04 Oct 2002 19:53:54 -0700
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2

Bryan Wagstaff <bryanw@xmission.com> writes:

> I'm confused about the 'saving the differences' issue.  Are we
> considering delayed delete, automatic versioning, both, or something
> else entirely?

If you are keeping versions, there is no reason you have to keep N
different copies of nearly-identical files (which seems to have been
one of your worries).  Instead, a clever implementation could keep
diffs (referring here to *concept* and not format).

> On one side I hear that we are saving diferences (versioning) and on
> the other I hear that we are only saving files opened with O_TRUNC,
> which are completely erased.  I think the issue isn't as hard as it is
> being made out to be.

"We are" doing nothing yet...

> [ I seem to remember that if a file was already opened, it couldn't be
> opened again with O_TRUNC | O_CREAT, open would return EACCES because
> the file is already being written to.  The excption of course was
> shared access and file locking, but that's another issue. ]

Your memory is incorrect.

> So one the one hand we WANT to save differences, as one would do with
> a versioning, but on the other hand we NEED to process the file in
> Posix fasion, which allows for an undelete.  I thought this thread
> decided earlier that delayed delete was the goal, and we were
> examining cases for applications not written to use an undelete
> library or API.  

I don't think this thread has "decided" anything; some people want
undelete (which Roland rightly points out should be called "delayed
delete"), others want file versioning, others want other things.

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