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Date:      Wed, 24 Mar 1999 10:45:40 +1030
From:      Greg Lehey <grog@lemis.com>
To:        Ludwig Pummer <ludwigp@bigfoot.com>, Codeguy <codeguy@wolf.com>, freebsd-questions@FreeBSD.ORG
Subject:   Re: Beginner questions re. vinum
Message-ID:  <19990324104540.N425@lemis.com>
In-Reply-To: <4.1.19990323151418.00b36ee0@mail-r>; from Ludwig Pummer on Tue, Mar 23, 1999 at 03:28:09PM -0800
References:  <199903232227.OAA19794@wolf.com> <4.1.19990323151418.00b36ee0@mail-r>

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On Tuesday, 23 March 1999 at 15:28:09 -0800, Ludwig Pummer wrote:
> At 02:27 PM 3/23/99 , Codeguy wrote:
>> I've currently got 1.2 GB of each drive allocated;
>> swap apace and root FS on da0, and /work on da1.
>> I'd like to use the remaining 3.3 GB of each drive
>> for vinum volumes.  Any reasons why I shouldn't be
>> able to do so?
>
> By unallocated, you mean not allocated in a slice, or not allocated in a
> partition? (Did you leave it empty when you were using sysinstall's fdisk
> or sysinstall's partition editor ?)
>
>> I *have* read through the man pages (I've got hard copy
>> here in front of me), and think I have an idea of how to
>> proceed.  I've created a file named /etc/vinum.rc, containing:
>>
>> drive drive0 device /dev/da0
>> drive drive1 device /dev/da1
>
> This tells vinum to use all of both SCSI disks. Including the 1.2GB of
> already-allocated space.

Oops, I missed this one.  Yes, Ludwig's right.  Use something like
/dev/da0e and /dev/da1e.  This probably also explains the messages you
have been getting.

> If the unallocated space wasn't assigned a slice, run fdisk to add a slice
> for it, create a partition which takes the entire disk using disklabel, and
> change the devices to be /dev/da0s2e or something similar.

To avoid shooting yourself in the foot, use the compatibility slice
/dev/da0e (at least for the present), since that's what vinum looks
for in the 'start' command.  I saw a case yesterday where somebody
hadn't created device nodes for the compatibility slices, so 'vinum
start' silently ignored the disks.

>> volume www
>>  plex org striped 256k
>>      sd length 1600m drive drive0
>>      sd length 1600m drive drive1
>> volume logs
>>   plex org striped 256k
>>      sd length 1600m drive drive0
>>      sd length 1600m drive drive1
>
> This does not mirror data. What this does is say that for each volume, you
> will have one plex (one copy of the data) split across the two drives. If
> you re-read the vinum manpages, you will see a sentence saying something
> like "a plex contains the entire address space of the volume...". If you
> want to have 2 copies of your www data, you need to make 2 plexes for each
> volume, not 2 subdisks for each plex. So the config becomes:
>
> volume www
>   plex org concat
>       sd length 1600m drive drive0
>   plex org concat
>       sd length 1600m drive drive1
> volume logs
>   plex org concat
>       sd length 1600m drive drive0
>   plex org concat
>       sd length 1600m drive drive1

This doesn't stripe, of course, but it's equally valid.

>> I assume this indicates that I did something majorly dumb.
>> Could some kind soul please point out the error of my ways?
>
> Yes. It's complaining that it can't write to the entirety of you da0 and
> da1 disks (probably because FreeBSD won't let it because you have mounted
> filesystems there).

I'm not sure how you managed to avoid shooting yourself in the foot,
but you're lucky, and I don't want to repeat the experiment here :-)

> I don't know too much about exactly when FreeBSD would stop vinum from
> writing to da0... some parts of the disk may have already been overwritten
> and you just haven't noticed yet (i'm thinking the boot sector/boot
> loaders). Greg, please correct me here.

In principle you're correct, but vinum turns this protection off :-)

Greg
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