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Date:      Mon, 1 Nov 1999 12:04:41 -0500
From:      Greg Lehey <grog@lemis.com>
To:        Alfred Perlstein <bright@wintelcom.net>, Greg Skouby <gskouby@ns0.sitesnow.com>
Cc:        freebsd-questions@FreeBSD.ORG
Subject:   Re: vinum RAID-5 again
Message-ID:  <19991101120441.40752@mojave.sitaranetworks.com>
In-Reply-To: <Pine.BSF.4.05.9910312357310.12797-100000@fw.wintelcom.net>; from Alfred Perlstein on Mon, Nov 01, 1999 at 12:00:00AM -0800
References:  <Pine.BSF.4.10.9911010103400.80104-100000@ns0.sitesnow.com> <Pine.BSF.4.05.9910312357310.12797-100000@fw.wintelcom.net>

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On Monday,  1 November 1999 at  0:00:00 -0800, Alfred Perlstein wrote:
> On Mon, 1 Nov 1999, Greg Skouby wrote:
>
>> Hello,
>> 	I got this sample RAID-5 config off of lemis.com/vinum and it
>> seems over simplified to the point where I don't think I understand it. If
>> at any time in this message you think I need to go back and RTFM please
>> stop reading and let me know that. This is the sample config for RAID-5
>> that I am referring to:
>>
>> drive e device /dev/da6h
>> volume raid5
>>   plex org raid5 512k
>>     sd length 128m drive a
>>     sd length 128m drive b
>>     sd length 128m drive c
>>     sd length 128m drive d
>>     sd length 128m drive e
>>
>>
>> I have a couple of questions about this. Is this config only slicing up
>> one drive? That is what I gather from the config but the theory behind
>> RAID-5 is that you need at least 3 for there to be a point in using
>> RAID-5. So one of my many questions is that where do the drive a, drive b,
>> drive c, drive d, and drive e 's come from? Are there seperated
>> statements for those devices like there is for the drive e? Something such
>> as  drive a devide /dev/da0h?
>
> I think there is an implied
>
> drive a device /dev/da2h
> drive b device /dev/da3h
> drive c device /dev/da4h
> drive d device /dev/da5h
>
> before the "drive e device /dev/da6h" line.
>
> it should be noted that some of the shortcuts used in the vinum manpage
> that aren't noted as being shortcuts can make things confusing for the
> first time user.
>
> the "drive" commands just provide a meaningful alias to /dev/ entries.

In particular, it allows you to move drives around physically.  Vinum
will still find them when starting up, thus removing a potential way
of shooting yourself in the foot.

Greg
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