From owner-freebsd-isp Tue Jan 26 06:45:55 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id GAA12606 for freebsd-isp-outgoing; Tue, 26 Jan 1999 06:45:55 -0800 (PST) (envelope-from owner-freebsd-isp@FreeBSD.ORG) Received: from mercury.webnology.com (mercury.webnology.com [209.155.51.2]) by hub.freebsd.org (8.8.8/8.8.8) with ESMTP id GAA12587 for ; Tue, 26 Jan 1999 06:45:50 -0800 (PST) (envelope-from jooji@webnology.com) Received: from localhost (jooji@localhost) by mercury.webnology.com (8.9.2/8.9.2) with SMTP id IAA08080; Tue, 26 Jan 1999 08:47:30 -0600 (CST) Date: Tue, 26 Jan 1999 08:47:30 -0600 (CST) From: "Jasper O'Malley" To: Greg Lehey cc: John Saunders , freebsd-isp@FreeBSD.ORG Subject: Re: ccd and vinum In-Reply-To: <19990126122753.B66239@freebie.lemis.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-freebsd-isp@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org On Tue, 26 Jan 1999, Greg Lehey wrote: > Ah. What you're saying is that each LP also has the same storage size > as a PP (4 MB), and that you're combining a number of them to make up > the size of the LV? Bingo. > OK. We're looking at this from a different side. If I've understood > you correctly, a 16 MB mirrored LV would look like: [diagram snipped] Yes, that's it. > In Vinum, a 16 MB mirrored volume made of 4 MB subdisks might look > like this: Ahhhhhhhhh. I think I've got it. > The result is the same, but the concept of plexes is pretty much the > opposite of the concept of LPs. In particular, I don't see how you > can stripe effectively with the LVM approach. It's bloody weird, actually. I've never quite understood it myself. Basically, the LVM breaks up the the PP into even smaller blocks, and stripes across PPs with those itty-bitty blocks: PP1-IBB1 --> PP2-IBB1 --> PP3-IBB1 --> PP1-IBB2 --> PP2-IBB2 --> etc. where IBB stands for "itty-bitty block," of course. > This diagram should also answer your question above: plexes contain > one or more subdisks. > > > and whether or not two plexes of a particular volume must take up > > the same number of subdisks (or have roughly the same subdisk > > layout, at least). > > No. There's no constraint there. So I can have one plex contained entirely within a single subdisk, and a second plex spread across two (or more) subdisks? Cheers, Mick The Reverend Jasper P. O'Malley dotdot:jooji@webnology.com Systems Administrator ringring:asktheadmiral Webnology, LLC woowoo:http://www.webnology.com/~jooji To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message