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Date:      Sun, 15 Oct 2000 15:54:42 -0500
From:      "Jim C. Nasby" <jim@nasby.net>
To:        Bennett Hui <bhui@mail.com>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: RAID 5 with Vinum
Message-ID:  <39EA1992.62F6FCC0@nasby.net>
References:  <NDBBKCNFGLGFDJGFGEECKEOBCDAA.bhui@mail.com>

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I don't see a reply from Greg, so I'll try and fill his shoes a bit.

Bennett Hui wrote:
> 
> I'm thinking about setting up a RAID 5 system with Vinum using 4 IDE HDDs.
> I've looked through the man pages on vinumvm.org, but I still have one
> preliminary question:

It's worth mentioning that you really don't want to create any plexes that
address two drives that are on the same IDE controller. IDE can't handle
concurrent requests, so you end up waiting for one drive to finish before
you can even tell the next drive what to do. Either use 4 seperate IDE
controllers, or SCSI.
 
> when installing FreeBSD with the intention of setting up RAID 5 using Vinum
> on 4 hard drives, do I install the whole OS on one hard drive and then use
> Vinum to arrange the file system on the remaining 3 hard drives, or do I
> install the OS on all 4 hard drives (assign space that fills up all 4
> drives) and use Vinum to work out the RAID 5 itself afterwards?

You can install almost the entire OS under a vinum volume; the notable
exception is /. You need / to get the kernel up and running, and you need
the kernel to be able to talk to a vinum volume. This is something that Greg
wants to change, but there's no ETA.
 
> One other question about Vinum I have:
> 
> If I have the FreeBSD OS on 2 hard drives without any RAID/Vinum setup and
> then decide to add two more hard drives and setup RAID 5, is this something
> that Vinum can easily do, or is it easier to reformat all 4 drives and start
> from scratch?  If Vinum can do this "on the fly," what Vinum commands/steps
> would I use to do it?

Vinum can't currently resize a RAID5 volume, but even if it could, newfs
can't change the size of an existing filesystem, so you're still stuck with
moving all your data and recreating that volume. Note that you do *not* need
to 'format' the actual drives though; this kind of change can be handled
entirely by vinum.
 
> Thanks.
> 
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-- 
Jim C. Nasby (aka Decibel!)                                  /^\ 
jim@nasby.net                                               /___\
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