From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pieter De Wit Subject: Re: Looking for help how to migrate 2disk RAID1 to 3 disk RAID6 Date: Thu, 02 Jan 2014 11:06:03 +1300 Message-ID: <52C4914B.90301@insync.za.net> References: <1388537511.5058.22.camel@oxygen.netxsys.com> <52C36908.2010701@insync.za.net> <1388552041.5058.25.camel@oxygen.netxsys.com> <52C3EEE2.10402@insync.za.net> <1388589051.5058.43.camel@oxygen.netxsys.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1388589051.5058.43.camel@oxygen.netxsys.com> Sender: linux-raid-owner@vger.kernel.org To: Krzysztof Adamski Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 2/01/2014 04:10, Krzysztof Adamski wrote: > On Wed, 2014-01-01 at 23:33 +1300, Pieter De Wit wrote: > > Based of what you are saying you probably would not believe that RAID5 > can be made with 2 drives, DATA + 1 PARITY. But Linux RAID supports that > just fine (thanks Neil). Yeah - you right there - I can't see why you would have a "RAID1 set with parity", nor can I see how the calculations would work. Then again, I am not a MD developer and I am not going to look at the source code. I would like to know what the command line would look like to create this, for educational purposes. > Hot spares are a joke, you have to wait for a drive to fail before you > use them, that can be to late. A 3 drive RAID1 make more sense. On one > system I have a 8 drive RAID1 (the /boot partition) the / (root) > partition is a 8 drive RAID6. > > IMHO, you have answered your question of what RAID level you need to run, RAID1. As for your original question of the data migration, I would move the data over on a filesystem level. I used to have this neat trick where by I created soft symlink between the "new" and "old" locations, from memory, it only works between different block devices. You then instruct linux to copy the data to "itself". Since it's a symlink it copies the data to the new device. It was something along those lines. You need to mount the source as read only, iirc. Contact me off list if you want more details. Cheers, Pieter