Date: Sun, 27 Jan 2002 19:19:23 -0600 From: "Mike Meyer" <mwm-dated-1012612764.6cb45d@mired.org> To: Matt Penna <mdp1261@ritvax.isc.rit.edu> Cc: questions@freebsd.org Subject: Re: dump, restore - active vs. inactive filesystem Message-ID: <15444.42779.986980.179495@guru.mired.org> In-Reply-To: <121485656@toto.iv>
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Matt Penna <mdp1261@ritvax.isc.rit.edu> types: > Now here's my question - is "active filesystem" a technical term that has a > specific meaning? Yup. An actife file system is being changed. > Or does it just refer to any filesystem that is in use? Only if that usage includes writing to it. > Neither the dump nor the restore man pages explain exactly what is meant by > "active filesystem" or "inactive filesystem," and they don't seem to > explain how to prevent this problem of files not actually being copied to > tape. (Unless I'm missing it somewhere.) > > Does mounting a filesystem read-only mean it's inactive? (I suspect not.) A file system mounted read-only is inactive. > What exactly needs to be done to a filesystem prior to a level 0 dump to > ensure everything is backed up? You have three options. 1) Unmount the file system. 2) Mount the file system read-only. 3) Dump it in single-user mode, making sure nothing else is going on on the system. > In the dump man page, in the section where > the Tower of Hanoi algorithm is explained, it is implied that subsequent, > incremental backups can be performed on active filesystems without trouble. You're right, it does - but that's not true. You have the same problem that you do with full dumps: files changing during aren't properly on the backup tapes. The problem isn't quite as bad for daily dumps, as the dumps are typically much shorter than full dumps. Also, the normal worst case is that you've lost a day of work on that file. The real gotcha is if a file is modified daily at the same time as backups are run. That means it isn't on any daily tapes at all. <mike -- Mike Meyer <mwm@mired.org> http://www.mired.org/home/mwm/ Independent WWW/Perforce/FreeBSD/Unix consultant, email for more information. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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