Date: Thu, 27 Jul 2000 17:00:25 +0930 From: Greg Lehey <grog@lemis.com> To: Jack Rusher <jar@integratus.com> Cc: mjacob@feral.com, freebsd-arch@FreeBSD.ORG Subject: Re: SANs, disks, & devfs Message-ID: <20000727170025.E36365@wantadilla.lemis.com> In-Reply-To: <397CABB4.1CAAC7C3@integratus.com>; from jar@integratus.com on Mon, Jul 24, 2000 at 01:48:52PM -0700 References: <Pine.BSF.4.10.10007240442030.55035-100000@beppo.feral.com> <397CABB4.1CAAC7C3@integratus.com>
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On Monday, 24 July 2000 at 13:48:52 -0700, Jack Rusher wrote: > Matthew Jacob wrote: >> >> I think that vinum is already good, like VxVM also, in that once you label a >> disk (i.e., borg it into vinum), it's boot-time to boot-time address becomes >> can become less relevant. > > Yes, there is self descriptive meta data on VxVM and vinum drives. > However, you need some way to tell vinum which drives to eat. Vinum eats the drives it finds. When it's started, it goes looking for all partitions with partition type "Vinum", and it gets the name from the Vinum label. >> I think that the constancy of the /dev/daX namespace is relevant only as >> long as that is the name in /etc/fstab. > > There are other issues having to do with what happens when you pull a > disk out and copy the contents onto another drive (upgrade to bigger > primary disk, for instance). You want to just stick the drive back in > the machine and have everything boot and work normally. This only works > if the fstab looks at the first SCSI drive by a positional name. > > The other option is to use disklabels (instead of disk serial numbers) > to identify the disks. You can provide a label copy tool to clone a > disk, but you run into trouble when you have two disks that are clones > of one another in the same system. Vinum solves this position by taking the most recent label. Vinum labels include a "last modified" field. > You also have trouble if one of the disks is the > Windows/Linux/whatever partition of your workstation and has a label > scheme that doesn't play nice with the BSD scheme. What do you call > that disk in the device tree? You need both possibilities. It would be simple enough to allow both device names (with explicit pathname) and volume names (without) in /etc/fstab. > All I am trying to illustrate here is that there are some cases > where it is better to have absolute names and some cases where > positional abstraction is the right answer. It would be nice if we > could have a compromise of the two techniques that lets you look at > your storage in the way that makes the most sense for your > application. Agreed. Greg -- Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-arch" in the body of the message
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