From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Anderson Subject: Software RAID within RAID Date: Fri, 25 Jul 2003 03:48:42 +0200 Sender: linux-raid-owner@vger.kernel.org Message-ID: <20030725034842.52114001.david.anderson@calixo.net> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Hi all, First of all I would like to thank the developers of the linux software RAID system for their excellent work which has saved my data on several occasions. Recently I lost one of the disks on my software RAID5 (3x2Gb SCSI on a 2.4.21 Debian Woody). Seeking replacements, I came across two 4Gb SCSI drives. After inserting one of them as a temporary replacement for the dead 2Gb, I am now looking into ways of better integrating these two new disks into my existing setup. The most best solution I came up with was to extend the array's overall capacity from 4 to 8Gb. To do this I would first combine the two remaining 2Gb disks into a RAID0 array, and then combine that array and the two 4Gb disks into a RAID5 array. To clarify this, here is a diagram of this solution: http://polaris-outpost.net/vrac/Solution.png . However, there are a few things I would like to know before I make an attempt at this setup. First of all, would the software-raid driver handle disk failures properly even with the RAID within RAID? I do not see why not, but I'd rather be sure before I jump... The other question I have is about performances. Would the RAID0 array significantly impact on the overall I/O perfomances of the RAID5 array? If anyone has already had the opportunity of comparing performances on a regular RAID5 and a RAID5 containing a RAID0, I would be interested in the results. I will of course conduct my own tests once this setup is in place. Thanks in advance for your help David Anderson