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Date:      Tue, 11 Nov 2003 22:44:01 +0000
From:      Chris Howells <howells@kde.org>
To:        Greg 'groggy' Lehey <grog@FreeBSD.org>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: Vinum and reserved space
Message-ID:  <200311112244.07002.howells@kde.org>
In-Reply-To: <20031111221631.GL77527@wantadilla.lemis.com>
References:  <3189.192.168.1.104.1068570867.squirrel@sauron> <20031111221631.GL77527@wantadilla.lemis.com>

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Hi,

Thanks for the reply.

On Tuesday 11 November 2003 22:16, Greg 'groggy' Lehey wrote:

> > I've just bought 2 x 160GB drives which I want to RAID 1 with vinum. I
> > used /stand/sysinstall to fdisk and disklabel them, mounted them as
> > /temp1 and /temp2 and checked the size of them using 'df' to stick into
> > my vinum.conf file.
> >
> > I'm a bit confused though; the output of df does not include the 8% or
> > whatever of the slice that is reserved for root by default.
>
> It looks like it to me.

What I mean is that e.g. in the output from df:

/dev/vinum/sauron1 149118276     9447 137179367     0%    /vinum

the 149118276 (k) is the total size of the disk, whereas the 137179367 is t=
he=20
available space ( 149118276 - (8% of 149118276)).

I was following the instructions in the Absolute BSD book which now that I'=
ve=20
done it I think is confusing.

> You're confusing Vinum and UFS.  Vinum is a virtual disk.  UFS is a
> file system.  It's UFS which reserves 8% or so of the file system (not
> of the slice, which is a term which relates neither to UFS nor to
> Vinum).  If you reserve space on the disk and don't give it to Vinum,
> Vinum doesn't use it.  Period.

Right. My confusion was on how to determine the size of the slice to stick=
=20
into the vinum.conf file... According to Absolute BSD, the right thing to d=
o=20
is to read the 137179367 column, and use that value in vinum.conf. But=20
obviously that isn't using the whole disk because it does not include the 8=
%=20
of the drive that is set aside for root.

In all the example vinum.conf files that I could find, there was a hard-cod=
ed=20
size of the vinum drive.

Now I think about it more it's obvious. I think.

> That's because you haven't used all the space.  If the drives are the
> same, use 'length 0' for the subdisks and you'll get all the space in
> the volume.

Aha. I didn't know that you could set 'length 0', didn't see that documente=
d=20
anywhere. That solves all my problems since I don't need to determine the=20
size manually now. Thanks!

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Cheers, Chris Howells -- chris@chrishowells.co.uk, howells@kde.org
Web: http://chrishowells.co.uk, PGP ID: 0x33795A2C
KDE/Qt/C++/PHP Developer: http://www.kde.org
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