From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phil Turmel Subject: Re: Converting 4 disk RAID10 to RAID5 Date: Mon, 26 Oct 2015 10:10:37 -0400 Message-ID: <562E345D.5030206@turmel.org> References: <562D8142.80507@websitemanagers.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <562D8142.80507@websitemanagers.com.au> Sender: linux-raid-owner@vger.kernel.org To: Adam Goryachev , linux-raid@vger.kernel.org List-Id: linux-raid.ids Good morning Adam, On 10/25/2015 09:26 PM, Adam Goryachev wrote: > Hi all, > > I'm trying to convert a 4 disk RAID10 to a RAID5. Currently I have: > cat /proc/mdstat > Personalities : [raid10] > md0 : active raid10 sdd1[2] sdc1[1] sdb1[0] sde1[3] > 7813772288 blocks super 1.2 512K chunks 2 near-copies [4/4] [UUUU] > bitmap: 0/59 pages [0KB], 65536KB chunk [trim /] Your plan looks reasonable, if a bit long. I've done similar before. Usually I add the new array to the LVM volume group of the original, then pvmove the contents to the new physical volume. Let's me stay online through the entire operation. Anyways, it seems you are missing an opportunity to convert in place, though. Consider setting up four small loop devices and test conversions from r10,n2 -n4 => r0 -n3 => r4 -n4 => r5 -n4 . I suspect you can get to your new raid5 without moving a bunch of data around. Phil