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Date:      Tue, 2 Nov 1999 19:16:55 -0500 (EST)
From:      Kelly Yancey <kbyanc@posi.net>
To:        Bernd Walter <ticso@cicely.de>
Cc:        Rodney <rr@xs4all.nl>, freebsd-fs@FreeBSD.ORG
Subject:   Re: feature list journalled fs
Message-ID:  <Pine.BSF.4.05.9911021900030.3164-100000@kronos.alcnet.com>
In-Reply-To: <19991103005415.A88044@cicely7.cicely.de>

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On Wed, 3 Nov 1999, Bernd Walter wrote:

> On Tue, Nov 02, 1999 at 12:35:53PM -0500, Greg Lehey wrote:
> > On Sunday, 31 October 1999 at 12:05:14 +0100, Rodney wrote:
> > >
> > >
> > > hi,
> > >
> > > here's my list of features I'd like to see in a
> > > journalled fs. Have to admit this list is heavily
> > > inspired ( ok , copied ) from the VxFS features,
> > > apart from th buzz words,
> > > some of them make sense, some of them don't
> > > but it should give us some stuff to discus:
> > > [snip]
> > > 6) vinum integration (vague)
> > 
> > Vinum is just a virtual disk.  As such, any file system should work on
> > it.
> > 
> It is more than that - it is a volume manager.
> Maybe you are not clear how far you got beyound the virtual disk.
> It manages disks and can find it's drive properly if they changed devices - 
> that's working relay fine that I was able to remove nearly all wire
> configurations for drives and I'm eaven run a volume with only one single
> drive plex - just to get this feature.
> It can (or should be able to) resize a volume and should inform the system
> about.

  I am under the impression that you can only enlarge a vinum volume if it
in a RAID 0 configuration (concatenation). Obviously, it would be very
difficult to enlarge a RAID 1 or RAID 5 configuration as it would require
restriping the data across all disks; I'm not familiar with any product,
hardware or software, that can do this.
  Besides the fact that this would be an issue for any RAID controller
also. Anyone with a RAID controller can add a new disk to their RAID 0 and
enlarge the virtual disk. Those controllers aren't going to tell you about
the increased disk size any more than vinum does. Beyond that, who is to
say that the entire size of the new, enlarged, virtual disk is supposed be
dedicated to FFS. Is it not possible, however unlikely, for a sysadmin to
add disk space to a RAID array and partition it as say FAT32?

  I think what Greg was getting at as far as the file system is concerned,
vinum just looks like a disk. Whatever else vinum may be, to the file
system it just looks like a disk.

> I have some ideas about how to get FFS resizeable without needing to freeze or
> umount it before and without loosing inodes.

  This is great, but I think that "vinum hooks" are no more needed than
"ccd hooks" or "DPT hooks". User-land tools should allow the administrator
to resize the file system at the administrators discretion. Beyond the
technical issues of providing hooks to automatically extend file systems,
there is the social implication of whether that is what the user wanted.
User-land tools solve both problems.

> Vinum is the frontend for managing the size of the volume and it should inform
> the fs driver about any change, because there is no need to manualy call an
> additional tool.
> My point is modifying FFS but that's the same for any fs.
> 
> 

  No (see above). Forget about vinum, just worry about disks. Vinum will
play nice and pretend to be a disk. In the end you will have a cleaner
solution that plays nice with others too. Everyone will love the fact that
they can extend any disk, at command, either by adding drives to their
vinum config, their hardware RAID array, or finally whiping Windows off
their home system.

--
Kelly Yancey  -  kbyanc@posi.net  -  Richmond, VA
Director of Technical Services, ALC Communications  http://www.alcnet.com/
Maintainer, BSD Driver Database       http://www.posi.net/freebsd/drivers/
Coordinator, Team FreeBSD        http://www.posi.net/freebsd/Team-FreeBSD/



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