Date: Mon, 1 Nov 1999 12:03:38 -0500 From: Greg Lehey <grog@lemis.com> To: Greg Skouby <gskouby@ns0.sitesnow.com>, freebsd-questions@FreeBSD.ORG Subject: Re: vinum RAID-5 again Message-ID: <19991101120338.43152@mojave.sitaranetworks.com> In-Reply-To: <Pine.BSF.4.10.9911010103400.80104-100000@ns0.sitesnow.com>; from Greg Skouby on Mon, Nov 01, 1999 at 01:11:19AM -0500 References: <Pine.BSF.4.10.9911010103400.80104-100000@ns0.sitesnow.com>
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On Monday, 1 November 1999 at 1:11:19 -0500, 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
OK, what you have here is a partial config, probably from the section
which explains that we're building up on existing configs. You're
missing the definitions for drives a to d, which were in earlier
examples.
> I have a couple of questions about this. Is this config only slicing up
> one drive?
No, it's slicing 5 drives.
> 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.
Correct.
> 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?
When starting from scratch, the complete config file might be:
drive a device /dev/da2h
drive b device /dev/da3h
drive c device /dev/da4h
drive d device /dev/da5h
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 guess I am just confused. Let me hit you up with the scenario that I am
> trying to use RAID-5 in. I have 4 external seagate drives of 23gigs each.
> I want to use those 4 drives in a RAID-5 array. They are da0 through da3.
> The drive where the OS sits is da4. I am wondering what I need to do to
> get RAID-5 running across those four drives. Thanks for all of your help.
> I appreciated it.
Just change the numbers and remove a drive (since you only have 4
available):
drive a device /dev/da0h
drive b device /dev/da1h
drive c device /dev/da2h
drive d device /dev/da3h
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
Greg
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