From mboxrd@z Thu Jan 1 00:00:00 1970 From: Adam Goryachev Subject: Re: Resurrecting a Dirty RAID-5 Date: Mon, 13 Jul 2015 08:33:09 +1000 Message-ID: <55A2EB25.10607@websitemanagers.com.au> References: <559D2374.7040208@turmel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: jtroan@jt-sw.com, Mikael Abrahamsson Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 13/07/15 01:01, jtroan@jt-sw.com wrote: >> On Wed, 8 Jul 2015, jtroan@jt-sw.com wrote: >> >>> I'm also thinking about adding a fourth drive and try to config it as a >>> hot-spare, giving me some extra margin for failure. >> I would recommend you turn your raid5 into raid6 instead of having a >> raid5+spare. This can be done with a fairly simple command, without >> downtime. >> > I like the idea of using RAID-6 for / (for all the VMs under /var). (I > figure I'll probably still have to do a spare on my RAID-1 device > for /boot .) > > What's the (mdadm?) command to convert an MD from RAID-5 to RAID-6? > I think the standard option would be to have a hot spare, and then something like: mdadm /dev/mdX --grow --level=raid6 Also, for your raid1, never have a hot spare, just do this: mdadm /dev/mdX --grow --raid-devices=3 Then you will always have all your data replicated on all three drives, so again, no hot spare required. Also remember to duplicate the grub/whatever boot sector.... Regards, Adam -- Adam Goryachev Website Managers www.websitemanagers.com.au