freebsd-questions Digest, Vol 12, Issue 2

J. Seth Henry jshamlet at
Mon Jun 9 12:37:11 PDT 2003

Actually, this should work, but it will require some twiddling with the
disks partition table in disklabel. I used to have an old drive array with
a bunch of HP labelled Seagate ST32550WD drives. For some unearthly
reason, some of the drives were formatted to have only 2 billion bytes
(2000MB), not 2GB (2047MB). I was able to get the array going by manually
altering the partition tables on the larger drives to match the smallest
drives. The rest of the space was left unformatted, and the array worked
just fine.

I later figured out how to load new firmware in the drives, and low-level
formatted them all to match - but for about a month I had the array going
with the mix-and-match.

In this case, you will only have to muck with the partition table on the
one disk, since it is bigger than the rest. First, create at least two
partitions on the disk, filling the entire space. Then, use disklabel to
get the paramaters for one of the 120's. Write all this down, and then use
diskabel to make the FIRST partition on your 170 match. You will need to
do some math to calculate the paramters for the second partition, but it
isn't too hard. As a bonus, you can even use this second partition while
the first partition is part of an array. Unfortunately, I don't believe
you can boot from this partition, but you could mount it as /usr or

If you really don't mind losing the 50Gb, you can just make the disklabel
info EXACTLY the same - but 50Gb is quite a bit of space to toss.

Keep in mind, this was a while back - probably 4 years, but I definitely
remember doing this. All the drives were SCSI, but that shouldn't matter
in this case.

Seth Henry

On Mon, Jun 09, 2003 at 05:10:37PM +0200 or thereabouts, Josh seemed to
> I have three 120GB disks and one 170GB disk. The first three is forming
> a raid-5 volume using Vinum and the last one is just fooling around
> without any purpose.
> Can I add this 170GB to the raid5 volume in any way at all? I do realise
> that I will loose 50Gb, but that's better than not using it at all.

Sorry, no.
On the other hand, if the first three were a concat plex, you *could* do
and you wouldn't even lose 50gb!
Your best bet is either:
a) mount the 170gb on /usr2 or something
b) backup the data on the raid5, restore to a concat

-- Josh

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