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Date:      Tue, 28 Sep 1999 15:58:27 -0400 (EDT)
From:      David Gilbert <dgilbert@velocet.ca>
To:        freebsd-stable@freebsd.org
Subject:   vinum experiences (not as documented, at least).
Message-ID:  <14321.7651.741516.883168@trooper.velocet.ca>

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OK... so I got FreeBSD out to play with for the first time in a long
while... to play with RAID.  It doesn't appear to work as advertied.

This weekend, I got three drives together to test vinum --- a
particular vinum configuration that I was trying to instruct someone
over a great distance to set up.  In particular, I wanted to have only 
root off of the raid (in the future, I might even have a mfsroot
kernel to eliminate the root failure point).  Of course, it would be
nice if you could boot with a raid root --- that doesn't seem too
far-fetched (but loading the kernel from a raid partition would be
hard, I understand), but this is what I was doing.

So I have 3 IDE disks (he's using SCSI, but I'm on a budget here ---
and I needed them today, not next week) on which I partition 128M
root on one, and 128M swap on the two others... then install just the
'bin' dist.

Then, I boot and edit the disklabels such that all three drives have
128M in a and the rest in g.  This is not very relavant, but is
background information.  The 3 'g' partitions are added as vinum
drives.  Then I vinum create a 'usr' volume that is RAID-5.

Now... If I put 'start_vinum="YES"' in rc.conf, everything works
fine.  However, if I boot normally, and then type 'vinum start'
afterwards, the machine panics.  This should be easy enough for you to 
reproduce.

The second buglet that I still havn't overcome (the above has the
obvious workaround) is that I did a 'vinum stop -f usr.p0.s2' ... to
test raid... and it did work just fine.  Then later, I did a 'vinum
start usr.p0.s2' ... and it told me that it was working on it, but it
would later fail.  Fail every time.  Even if the partition in question 
was unmounted, the rebuild would fail.

Later, I reread things and it appeared that detach/attach should work
on a subdisk.  This actually crashes the partition --- it doesn't work 
at all if I do that.  Attach will not allow me to add a subdisk to a
raid5 partion --- which is obviously what you'd need to do if you were 
replacing with hot-swap.

Dave.

-- 
============================================================================
|David Gilbert, Velocet Communications.       | Two things can only be     |
|Mail:       dgilbert@velocet.net             |  equal if and only if they |
|http://www.velocet.net/~dgilbert             |   are precisely opposite.  |
=========================================================GLO================


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