Date: Wed, 17 Mar 1999 08:52:24 +1030 From: Greg Lehey <grog@lemis.com> To: Brad Knowles <blk@skynet.be>, freebsd-questions@FreeBSD.ORG Subject: Re: Vinum questions? Message-ID: <19990317085224.W429@lemis.com> In-Reply-To: <19990216135911.003314@relay.skynet.be>; from Brad Knowles on Tue, Feb 16, 1999 at 01:59:11PM %2B0100 References: <19990316085422.F429@lemis.com> <19990216135911.003314@relay.skynet.be>
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On Tuesday, 16 February 1999 at 13:59:11 +0100, Brad Knowles wrote:
> On Tue, Mar 16, 1999, Greg Lehey <grog@lemis.com> wrote:
>
>> This is almost certainly bad advice. If there's an exception, it
>> would be nice to know the reasoning.
>
> Well, it wouldn't let me `disklabel -e` the disks in question,
What was the problem?
> so I wasn't able to create anything other than the "c" partition.
> If you're never going to fix it so that we can use the "c" partition
> with vinum,
I am not going to "fix" it because there is nothing to fix. It is
WRONG to use partition c for data storage, and I go to some lengths to
ensure you can't.
> then it would follow that the admin needs to be able to disklabel
> the drive(s) in question so as to create a partition that can
> actually be used with vinum.
Correct. I'm trying to find out why you can't do that, but you need
to give me some details.
> If the disk in question can be disklabelled and a filesystem created
> on the partition to be used with vinum, then you should also be able
> to use vinum on that partition to create subdisks, plexes, and
> volumes. Right?
Wrong. In order to create a file system, you need a partition of type
"4.2BSD". In order to create a vinum drive, you need a partition of
type "unused" or "vinum". This is an elementary protection against
wiping out data on the wrong disk, and it's described in vinum(8):
DRIVE LAYOUT CONSIDERATIONS
vinum drives are currently BSD disk partitions. They must be of type
unused in order to avoid overwriting file systems. In later versions of
vinum this requirement will change to type vinum. Use disklabel -e to ed-
it a partition type definition. The following display shows a typical
partition layout as shown by disklabel:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 81920 344064 4.2BSD 0 0 0 # (Cyl. 240*- 297*)
b: 262144 81920 swap # (Cyl. 57*- 240*)
c: 4226725 0 unused 0 0 # (Cyl. 0 - 2955*)
e: 81920 0 4.2BSD 0 0 0 # (Cyl. 0 - 57*)
f: 1900000 425984 4.2BSD 0 0 0 # (Cyl. 297*- 1626*)
g: 1900741 2325984 unused 0 0 0 # (Cyl. 1626*- 2955*)
In this example, partition g may be used as a vinum partition. Parti-
tions a, e and f may be used as UFS file systems or ccd partitions. Par-
tition b is a swap partition, and partition c represents the whole disk
and should not be used for any other purpose.
vinum uses the first 265 sectors on each partition for configuration in-
formation, so the maximum size of a subdisk is 265 sectors smaller than
the drive.
>> your plex size is not a multiple of the stripe size, Vinum will trim
>> it for you.
>
> It will trim the plex size or the stripe size?
The plex size.
> And is a stripe size of 256-512KB still recommended for operations
> such as an anonymous ftp server?
Yes, for all applications.
Greg
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