From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [linux-lvm] Re: IBM to release LVM Technology to the Linux References: <200006182251.QAA15919@lynx.turbolabs.com> From: "Martin K. Petersen" Date: 21 Jun 2000 19:28:11 +0200 In-Reply-To: Andreas Dilger's message of "Sun, 18 Jun 2000 16:51:01 -0600 (MDT)" Message-ID: MIME-Version: 1.0 Sender: owner-linux-lvm Errors-To: owner-linux-lvm List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Andreas Dilger Cc: Linux LVM mailing list >>>>> "Andreas" == Andreas Dilger writes: Andreas> Having used both the AIX LVM, the Linux LVM, and the good-old Andreas> DOS partitions, I would have to disagree with your statement Andreas> that logical extents are of very little benefit. One of the Andreas> worst things to do in a DOS-partitioned world is to resize Andreas> the partitions themselves. You always have to over-estimate Andreas> the partition sizes in case you need more space in the Andreas> future, or add a whole new partition if you run out of space Andreas> in the existing partition. Andreas, you are preaching to the choir. Partitions don't belong in an LVM architecture at all. They are a legacy thing which needs to go away. Also, I don't tend to agree with most of the infrastructure proposed in the IBM whitepaper. If IBM's intention is that this will be a cross-OS LVM architecture, well then fine -- lots of abstractions are obviously needed. If it is supposed to be Linux specific, however, I don't see why one would waste engineering resources implementing plug-ins for reading Macintosh partitions types etc. We already have an adequate framework for that in the kernel. The scheme I've been toying with over the past months: - Logical Disk = Either partition or whole disk. - The Logical Disk provides allocation space for extents. - Extents are allocated on the available logical disks based upon heuristics in the feature set/system administrator preferences. - Logical Volume consists of one or more extents accessed through one or more feature sets (RAID0, RAID1, RAID5, encryption, whatever). The extents can be of varying size depending on the application. A 30 GB RAID5 LV could be constructed from 4 x 10 GB extents on 4 different physical disks + a 10 GB hot spare extent on a fifth disk, for instance. -- Martin K. Petersen Principal Linux Consultant, Storage http://mkp.net/ Linuxcare, Inc.