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RE: XFSDUMP and multiple filesystems on one tape

To: Russel Ingram <ringram@xxxxxxxxxxxxxx>
Subject: RE: XFSDUMP and multiple filesystems on one tape
From: ivanr@xxxxxxxxxxxxxxxxx (Ivan Rayner)
Date: Wed, 27 Jun 2001 15:27:29 +1000
Cc: "Gonyou, Austin" <austin@xxxxxxxxxxxxxxx>, Joshua Baker-LePain <jlb17@xxxxxxxx>, <linux-xfs@xxxxxxxxxxx>
In-reply-to: <Pine.LNX.4.33.0106262358140.1201-100000@xxxxxxxxxxxxxxxxxxxxx>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Wed, 27 Jun 2001, Russel Ingram wrote:

> On Tue, 26 Jun 2001, Gonyou, Austin wrote:
> > Will those actions yield a tape which only has the last dump on it, or will
> > it seek to the end of the last dump, and then start writing? If it does do
> > that, then I'm set. As I'm led to believe that it does from Steve Lord's
> > previous post. I just didn't see that behaviour with dump I don't think, so
> > I'm just skeptical without getting it substantiated first. Thanks for the
> > feedback.
>
> Doing it with that particular device will result in several dumps that
> overwrite each other (I'm pretty sure).  To be sure to avoid overwriting
> individual dumps use the non-rewinding device:

xfsdump will actually skip over dumps that may already exist on the tape.
The way it works is that it will read the tape and if it finds a dump, it
will skip past it and then do another read.  It will fail if it finds
something that is not a dump otherwise it will write after all the other
dumps.

Specifying '-o' (overwrite) disables this behaviour, causing xfsdump to
just write wherever the tape is positioned.

(If you find that xfsdump doesn't behave as advertised, please let us
know.)

> Now, since I just finally got a tape drive working on my Linux system with
> XFS, I have a quick question for the xfsdump folks.  xfsdump on Irix gives
> sort of a progress report with percent of job done.  Is there a reason
> this is no in the Linux version?

xfsdump on linux does not include threading, ie. it runs in a single
thread.  Progress reporting is a feature of xfsdump's multi-threaded mode.
The reason the Linux version is single threaded is simply that I was moved
onto other things before I finished the port.  The only real functionality
lost is the ability to write several tapes at once and it was felt that
this probably wouldn't be a big issue for the Linux folk at the moment.

Ivan

-- 
Ivan Rayner
ivanr@xxxxxxxxxxxxxxxxx


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