From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 24 Jul 2001 15:13:19 -0400 From: Jason Tackaberry Message-ID: <20010724151319.H25303@linux.com> Mime-Version: 1.0 Content-Disposition: inline Subject: [linux-lvm] LVM vs. md: Benefits in RAID0? Sender: linux-lvm-admin@sistina.com Errors-To: linux-lvm-admin@sistina.com Reply-To: linux-lvm@sistina.com List-Help: List-Post: List-Subscribe: , List-Unsubscribe: , List-Archive: List-Id: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-lvm@sistina.com I am about to be deploying a new server whose purpose is to replace an existing, aging system. The new server has 2 18GB drives. Once I migrate the user data to the new server, I can reclaim a practically brand new 18GB disk in the old server, bringing the total raw capacity to 18x3 GB. I installed RH7.1 and was happy to see how easy it was to setup mirroring using the md driver. My plan was to setup 9GB on each disk in a RAID1 config, and then stripe the remaining 9GB on each disk for user data in /home. Then, when I migrated the user data from the old server, I could add the 18GB into /home to give me 36GB for user data. (I want redundancy for the system partitions because as this is a mail server, I do not want the flow of mail to be interrupted during a disk failure. For user data I want to go for raw storage, since I will take full backups nightly.) In planning the migration, I discovered that md does not allow you to grow. Well, no problem, I know LVM supports this, so I setup LVM to stripe the 2 9GB partitions together. Then, I dropped a 3rd disk in to test the procedure of adding a new disk to the stripe set. I unfortunately then discovered LVM won't let you extend a RAID0 volume, but this is supposedly a planned feature for post-1.0. I assume the only way to proceed is to use linear concatenation. This lets me extend the volume, but then I don't get the performance gain I'd see with RAID0. But, as I understand the LVM, its advantage is that it lets you resize volumes. Since you can't currently do this in RAID0, does the LVM offer any benefits over md in this situation? Thanks, Jason. -- Academic Computing Support Specialist Assistant Section Editor Algoma University College http://linux.com/develop Sault Ste. Marie, Ontario 705-949-2301 x330 Personal Home Page http://www.auc.ca http://sault.org