From owner-freebsd-hackers Wed Apr 7 20:30:27 1999 Delivered-To: freebsd-hackers@freebsd.org Received: from peach.ocn.ne.jp (peach.ocn.ne.jp [210.145.254.87]) by hub.freebsd.org (Postfix) with ESMTP id 7547915238 for ; Wed, 7 Apr 1999 20:30:22 -0700 (PDT) (envelope-from dcs@newsguy.com) Received: from newsguy.com by peach.ocn.ne.jp (8.9.1a/OCN) id MAA24871; Thu, 8 Apr 1999 12:27:29 +0900 (JST) Message-ID: <370C1D6E.C447CB11@newsguy.com> Date: Thu, 08 Apr 1999 12:07:26 +0900 From: "Daniel C. Sobral" X-Mailer: Mozilla 4.51 [en] (Win98; I) X-Accept-Language: pt-BR,ja MIME-Version: 1.0 To: Greg Lehey Cc: Ollivier Robert , FreeBSD Hackers Subject: Re: Separate boot partition? References: <19990407085435.M2142@lemis.com> <19990407080113.A4122@keltia.freenix.fr> <19990407155835.M2142@lemis.com> <19990408000955.D8314@keltia.freenix.fr> <19990408095949.G2142@lemis.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Transfer-Encoding: 7bit Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Greg Lehey wrote: > > A lot of the differences are conceptual. What are volume groups? > They correspond in position to plexes, but I believe they're different > I think in IBM VGs (or whatever they're called there) contain the > replicated data for part of a volume. A plex contains one copy of the > data for the entire volume. A volume group is a collection of physical volumes. You can have it replicating a single physical volume two or three times (ie, two or three hd with replicated data). It cannot replicate data that spans more than one physical volume (ie, you can't have four physical volumes replicated 2-2). This replication feature is a minor feature, though. The main use of volume groups is in a collection of non-replicated physical volumes, over which you'll be allocating logical volumes. You can add and subtract physical volumes to/from a volume group. A volume group contains information about the logical volumes it's logical volumes and their mappings over the volume group (you can remap a logical volume -- moving it out of a disk you want to replace, for instance). It also has the "boot sectors". This information is replicated in each physical volume. It also has a, err, feature where you can specify a volume group automatically shuts down once the number of active physical volumes (and inactive one being one that crashed) gets below 50%. I wish my AIX books were not on the other side of the world... :-( -- Daniel C. Sobral (8-DCS) dcs@newsguy.com dcs@freebsd.org "nothing better than the ability to perform cunning linguistics" To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message