From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bill Davidsen Subject: Re: Two-disk RAID5? Date: Thu, 04 May 2006 21:22:29 -0400 Message-ID: <445AA8D5.2040604@tmr.com> References: <1146069707.10253.50.camel@kenny> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1146069707.10253.50.camel@kenny> Sender: linux-raid-owner@vger.kernel.org To: John Rowe Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids John Rowe wrote: >I'm about to create a RAID1 file system and a strange thought occurs to >me: if I create a two-disk RAID5 array then I can grow it later by the >simple expedient of adding a third disk and hence doubling its size. > >Is there any real down-side to this, such as performance? Alternatively >is it likely that mdadm will soon be able to convert a RAID1 pair to >RAID5 any time soon? (Just how different are they anyway? Isn't the >RAID4/5 checksum just an OR?) > I think it works, I just set up a little test case with two 20MB files and loopback mount. The mdadm seems to work, the mke2fs seems to work, the f/s is there. Please verify, this system is a bit (okay a bunch) hacked. -- bill davidsen CTO TMR Associates, Inc Doing interesting things with small computers since 1979