From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Pittman Subject: Re: RAID 5 questions Date: Sun, 01 Aug 2004 13:08:34 +1000 Sender: linux-raid-owner@vger.kernel.org Message-ID: <871xira72l.fsf@enki.rimspace.net> References: <1091325475.2374.11.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: To: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 1 Aug 2004, Ninti Systems wrote: > I'm about to embark on building a RAID 5 Linux software array with 4 > disks (I've only ever built 2 disk RAID 1 arrays before). > > Q1: Is it true that Linux can't/shouldn't boot off a RAID 5 array? Grub certainly can't boot of a software RAID-5 array, and I don't believe that lilo can either. This is because of these tools not understanding the RAID-5 disk layout, not any other limitation. > Q2: The four disks have identical manufacturer, model and size, but two > are brand new while two have had NTFS filesystems on them. Accordingly, > if I run hdparm -g on them, two disks have these specs: > > geometry = 2498/255/63, sectors = 40132503, start = 0 > > while the other two disks have these specs: > > geometry = 39813/16/63, sectors = 40132503, start = 0 > > Is this an issue with software RAID? No. Software RAID, unlike hardware raid, cares only that you have enough blocks on the disk. You don't need to match *any* other characteristic of the disks, and not even that if you don't mind wasting a few bytes. Daniel -- The PC is the LSD of the '90s. -- Timothy Leary, __Guardian_ (June 1, 1996)