From owner-freebsd-isp Mon Jan 25 06:55:03 1999 Return-Path: Received: (from majordom@localhost) by hub.freebsd.org (8.8.8/8.8.8) id GAA24959 for freebsd-isp-outgoing; Mon, 25 Jan 1999 06:55:03 -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 GAA24952 for ; Mon, 25 Jan 1999 06:55:01 -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 IAA19932; Mon, 25 Jan 1999 08:56:35 -0600 (CST) Date: Mon, 25 Jan 1999 08:56:35 -0600 (CST) From: "Jasper O'Malley" To: Greg Lehey cc: John Saunders , freebsd-isp@FreeBSD.ORG Subject: Re: ccd and vinum In-Reply-To: <19990125131628.C36690@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 Mon, 25 Jan 1999, Greg Lehey wrote: > I think it might be possibly better to say that you combine PPs to > make LPs, and LPs to make LVs. Sort of, but not quite. LVs are made up of LPs. But exactly how many PPs are in each LP of a particular LV depends on the "mirror" property of an LV. If it's not mirrored, there is exactly one PP per LP. If it's a simple mirror, there are exactly two PPs for each LP in the LV. If it's a double mirror, there are exactly three PPs for each LP in the LV. Each LP in a particular LV has the same number of PPs as every other LP in that LV. That's where the jump from "physical" to "logical" is made. > In this case, a PP corresponds to a > subdisk (but it's less flexible), an LP corresponds to a plex, and an > LV corresponds to a volume. I think I'm beginning to see the difference...in the LVM, PPs are used are used as simple building blocks, all of a uniform size. I can make a LV of any size I want (as long as it's a multiple of the PP size) by picking off PPs from anywhere within the VG. That's also how I can grow the filesystem, by simply adding more PPs (via LPs) to the LV. The only thing that's got me confused about Vinum is whether or not a plex has to exist within a single subdisk, or whether it can span 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). > I'm not sure this is stated correctly. I'd be more inclined to > expect: ``Mirroring is accomplished by assigning more that one LP to > an LV''. Nope. LVs are always made up of multiple LPs. Mirroring is accomplished by assigning more than one PP to each LP in an LV. Thanks for the explanation. 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