From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx3.redhat.com (mx3.redhat.com [172.16.48.32]) by int-mx1.corp.redhat.com (8.11.6/8.11.6) with ESMTP id j8EKKeV29987 for ; Wed, 14 Sep 2005 16:20:40 -0400 Received: from server6.hostpoint.ch (server6.hostpoint.ch [217.26.52.16]) by mx3.redhat.com (8.13.1/8.13.1) with ESMTP id j8EKKVeR030321 for ; Wed, 14 Sep 2005 16:20:32 -0400 Received: from 217-119-145-4.sefanet.ch ([217.119.145.4] helo=[192.168.15.41]) by server6.hostpoint.ch with esmtpa (Exim 4.43) id 1EFdkA-0003Ue-2O for linux-lvm@redhat.com; Wed, 14 Sep 2005 22:20:34 +0200 Message-ID: <43288600.7080501@markus.org> Date: Wed, 14 Sep 2005 22:20:16 +0200 From: Markus Baertschi MIME-Version: 1.0 Subject: Re: [linux-lvm] VGDA Question References: <20050907144600.42410.qmail@web52915.mail.yahoo.com> In-Reply-To: <20050907144600.42410.qmail@web52915.mail.yahoo.com> Content-Transfer-Encoding: quoted-printable Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="iso-8859-1"; format="flowed" To: LVM general discussion and development Rik Herrin wrote: >Hi, > According to the LVM man page, the VGDA (Volume Group >Descriptor Area) holds the metadata responsible for >keeping information about the LVs. However, it is >contained in the PVs. Why does the VGDA contain both >LV descriptors and PE descriptors? > Because there are LV's with PE's and both types of information must be=20 stores somewhere. > Shouldn't it just >have PE descriptors and leave the LV descriptors to >the volume group ? > The VGDA is where the volume group information is stored. The LV info is=20 therefore exactly where it belongs. > Also, when booting, what makes the >kernel know that there are VGs and LVs? > The vgscan command is run during boot (from a rc file) and it detects=20 the volumegroups and makes them available. > Does it look >at the type of the partition and if it detects that >it's a PV, extract the VGDA to help it build this >information? > Yes > If this is so, how does it deal with >entire harddisks. For example, if I run the command: >pvcreate /dev/sdd >how would the kernel know that this is a PV?.=20 > =20 > If you use the enire harddisk, then there is no traditional partition=20 table. In this case the vgscan command looks if the entire disk is a PV. >Finally, where exactly is the VGDA information held?. > At the beginning of the disk/partition you created with pvcreate. Markus --=20 Markus Baertschi Phone: ++41 (21) 807 1677 Bas du Ross=EF=BF=BD 14b Fax : ++41 (21) 807 1678 CH-1163, Etoy Email: markus@markus.org Switzerland Homepage: www.markus.org