Vinum and reserved space

[Chris Howells]

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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 the 
available space ( 149118276 - (8% of 149118276)).

I was following the instructions in the Absolute BSD book which now that I've 
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 
into the vinum.conf file... According to Absolute BSD, the right thing to do 
is to read the 137179367 column, and use that value in vinum.conf. But 
obviously that isn't using the whole disk because it does not include the 8% 
of the drive that is set aside for root.

In all the example vinum.conf files that I could find, there was a hard-coded 
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 documented 
anywhere. That solves all my problems since I don't need to determine the 
size manually now. Thanks!

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