From owner-freebsd-questions@FreeBSD.ORG Tue Apr 27 14:19:10 2010 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C591B1065694 for ; Tue, 27 Apr 2010 14:19:10 +0000 (UTC) (envelope-from pdegoeje@service2media.com) Received: from s2m-is-001.service2media.com (rev-130-102.virtu.nl [217.114.102.130]) by mx1.freebsd.org (Postfix) with ESMTP id 605F28FC2F for ; Tue, 27 Apr 2010 14:19:09 +0000 (UTC) Received: from pieter-dev.localnet ([10.0.1.77] RDNS failed) by s2m-is-001.service2media.com with Microsoft SMTPSVC(6.0.3790.3959); Tue, 27 Apr 2010 16:19:07 +0200 From: Pieter de Goeje Organization: Service2Media To: freebsd-questions@freebsd.org Date: Tue, 27 Apr 2010 16:19:06 +0200 User-Agent: KMail/1.12.2 (Linux/2.6.31-20-generic; KDE/4.3.2; x86_64; ; ) References: In-Reply-To: MIME-Version: 1.0 Content-Type: Text/Plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <201004271619.06491.pieter@service2media.com> X-OriginalArrivalTime: 27 Apr 2010 14:19:07.0394 (UTC) FILETIME=[98FD1E20:01CAE614] Cc: Eitan Adler Subject: Re: geom, glabel, and related terminology X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 27 Apr 2010 14:19:10 -0000 On Tuesday 27 April 2010 13:49:02 Eitan Adler wrote: > I'm a little bit confused about some of the file system terminology. > > What exactly is a GEOM label? A geom label is a name (hence label) for a GEOM provider. This label is interpreted/read by glabel(8). The source of the label can be the volume label or id of a filesystem, or a custom label created by glabel(8). > What does it mean to have one or for > one to be stopped? The underlying provider was mounted which causes the label to disappear (become unavailable). For example if we have a filesystem labeled "data" on /dev/ad1p7 it shows up as /dev/label/data in addition to /dev/ad1p7. When the user mounts /dev/ad1p7 the label disappears. > What is a GEOM provider? A GEOM provider is a piece of software/hardware which implements the common GEOM provider interface: it manifests itself as a device which supports read/write operations and a number of other common operations and transforms. Because all GEOM providers implement the same interface, a file system for example only needs to support the GEOM interface to support all storage hardware supported by FreeBSD. Because some providers are also consumers, GEOM classes can be stacked together to create advanced storage architectures. For example, two disks, both GEOM providers, can be consumed by a mirror GEOM class (gmirror(8)), which itself is just another provider which can be consumed by a filesystem or another GEOM consumer . > What is the difference between a bsd label and a geom label? Bsdlabel is the name of FreeBSD's old school partitioning system and tool (superseeded by gpart(8)). It is a layer above DOS partitions (slices in FreeBSD lingo). bsdlabel(8) supports 8 partitions per slice. A geom label is just another name for the underlying GEOM provider. > > If you could provide a high level overview the terminology it would > help me immensely. I hope this helps, - Pieter