From mboxrd@z Thu Jan 1 00:00:00 1970 From: NeilBrown Subject: Re: RAID5 -> RAID6 conversion, please help Date: Wed, 11 May 2011 10:21:16 +1000 Message-ID: <20110511102116.494bf0fd@notabene.brown> References: <002a01cc0f68$1c851180$558f3480$@priv.hu> <20110511093155.5b1a203e@notabene.brown> <4DC9CCAF.9010709@crc.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4DC9CCAF.9010709@crc.id.au> Sender: linux-raid-owner@vger.kernel.org To: Steven Haigh Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Wed, 11 May 2011 09:39:27 +1000 Steven Haigh wrote: > On 11/05/2011 9:31 AM, NeilBrown wrote: > > When it finished you will have a perfectly functional RAID6 array with full > > redundancy. It might perform slightly differently to a standard layout - > > I've never performed any measurements to see how differently. > > > > If you want to (after the recovery completes) you could convert to a regular > > RAID6 with > > mdadm -G /dev/md0 --layout=normalise --backup=/some/file/on/a/different/device > > > > but you probably don't have to. > > > > This makes me wonder. How can one tell if the layout is 'normal' or with > Q blocks on a single device? > > I recently changed my array from RAID5->6. Mine created a backup file > and took just under 40 hours for 4 x 1Tb devices. I assume that this > means that data was reorganised to the standard RAID6 style? The > conversion was done at about 4-6Mb/sec. Probably. What is the 'layout' reported by "mdadm -D"? If it ends -6, then it is a RAID5 layout with the Q block all on the last disk. If not, then it is already normalised. > > Is there any effect on doing a --layout=normalise if the above happened? > Probably not. NeilBrown