From mboxrd@z Thu Jan 1 00:00:00 1970 From: it Subject: block level vs. file level Date: Sun, 12 Feb 2006 11:31:07 -0800 Message-ID: <43EF8CFB.5080403@kfa.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Sender: linux-raid-owner@vger.kernel.org To: linux-raid@vger.kernel.org List-Id: linux-raid.ids Greetings, There seem to be two ways of doing software RAID, and I have had trouble finding information on this. First, the raid is done with partitions, for example /dev/sda1 and /dev/sdb1 are partitioned as Linux type and the mirroring is done then between the two partitions. The writing takes place on a filesystem level, and the partition table is not actually mirrored, because it's not on /dev/sda1 or /dev/sdb1. The hardware raid does the mirroring on the block level, so it's actually /dev/sda mirroring /dev/sdb - the whole drive, and not partitions. There is a way to set this up on software raid. It takes more configuration tweaking, but the mirroring then includes the partition table as well. This way, if a drive fails, one can replace it without pre-partitioning it. This also raises another point, which is relevant for both cases - same exact models of hard disks have different number of cylinders, so if a RAID partition is created on a larger drive it cannot be mirrored to a smaller drive. Does anyone have any experience with this? A.