I am going to the hacker archives before I make any more suggestions
however I wanted to be a little more clear about my previous question
(quoted below).
I was thinking of concattinating a min-number of chunks there where
sequentially stored on sequential amanda tape volumes, um, chunks
1-n on ARCH06 and n+1 to 99 on ARCH07. I wasn't taking into account
any of the RAIT-tape stuff, I was thinking sequentail usage of tapes
in a single drive.
> On Thu, May 15, 2003 at 10:22:20AM -0400, Matt Hyclak wrote:
> > On Thu, May 15, 2003 at 10:10:15AM -0400, Jon LaBadie enlightened us:
> >
> > > Implementing the ability to split a DLE across multiple tapes would
> > > continue a trend away from a feature of amanda that attracted me;
> > > the ability to recover a dump using standard, non-amanda tools.
> > > The RAIT driver was the first salvo to degrade this feature.
> > >
> >
> > I agree with the statement about RAIT, but if amanda were spreading chunks
> > accross tapes, how would that lose the ability to restore with standard
> > tools? All you need to do is dd the n chunks off the tape, concatenate them
> > together, and you have a complete {dump,tar,etc.} archive waiting to go, no?
> > I think that would be extremely useful, and not turn so many people away
> > from such a great program....
>
>
> And Brian Cuttler asked:
> >
> > Couldn't you still recover from amanda tapes if the data where
> > written in 'chunksize' bits across more than a single tape ?
> >
> > I mean, keep the chunks in order so you can find them, append them
> > together when writing the tape to limit the amount of reassembly
> > work. How are chunks re-assembled by taper now ?
> >
> > Couldn't we recover with "# dd" and "# cat >>" or would reassemble
> > need to be more complex than that ?
>
>
> Its not so much that you "couldn't". More the effort involved, where
> the required information would be kept, and would existing implementations
> be affected.
>
> I suspect that with judicious use of dd and cat, I could reassemble a
> 3 tape RAIT dump. Not sure I'd want to try.
>
> With the current scheme I've even done an emergency recovery of some
> files on a WinNT system that had some ported unix utilities.
>
> Consider a situation where you have no amanda installation and no
> amanda records, only a tape, working tape drive, and a unix system.
> And you are under pressure to recover a file before the boss goes home ;)
>
> I was thinking of things like:
>
> - how to know/where to keep the chunk size
> - how do you know the tape file continues on to the next tape
> - how do you deal with the partial last chunk on the first tape
> which is duplicated on the next tape
> - how will the file header on the second tape be different from
> a file header for the start of a dump, will that break anything
>
> Nothing insurmountable, but nothing as simple as position the tape,
> dd skiping one block, optionally uncompres, unarchive. And certainly
> not as simple to describe or include in the file header.
>
> --
> Jon H. LaBadie jon AT jgcomp DOT com
> JG Computing
> 4455 Province Line Road (609) 252-0159
> Princeton, NJ 08540-4322 (609) 683-7220 (fax)
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