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List:       linux-xfs
Subject:    Re: Is xfsdump operation atomic?
From:       Ivan Rayner <ivanr () sgi ! com>
Date:       2004-11-26 2:16:01
Message-ID: 20041126131601.355c0172.ivanr () sgi ! com
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On Wed, 24 Nov 2004 20:18:51 +0100, Michael Locher wrote:

> * What happens to existing files if they are modified (or their metadata
> eg. atime) is updated *exactly* when xfsdump is working on that file?
> (-> this is not yet cleared up. Maybe xfsdump could lock the file during
> dump?)

In that case your file may be inconsistent on tape.  However, because it
has been updated since xfsdump started (ie. its mtime > xfsdump time) it
will be included in tomorrow night's incremental dump.  If when you
restore you find the file in an inconsistent state, you can try restoring
the file from a previous dump.

I don't think you'd want xfsdump to block for an unknown amount of time on
a locked file.  If a file has a mandatory lock, xfsdump will skip it.

There are many ways to shoot yourself in the foot in Unix.  Sometimes it's
up to the user/admin to aim at something else.

> Another question: Can a frozen filesystem be dumped?

This may have changed in recent years, however back when I had something
to do with xfsdump, if you had quotas xfsdump created a quotas file in the
root of the dumped filesystem that would then be included in the dump.
This means that xfsdump will sometimes want to write to the filesystem. If
it can't write, xfsdump will probably just issue an error and continue. I
can't think of any other reason why you couldn't dump a frozen filesystem.

Ivan


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