Re: Feeback on RAID1 feature of Btrfs
From: Brendan Hide <hidden>
Date: 2012-12-18 11:50:27
On 2012/12/17 06:23 PM, Hugo Mills wrote:
On Mon, Dec 17, 2012 at 04:51:33PM +0100, Sebastien Luttringer wrote:quoted
Hello,
snip
quoted
I get the feeling that RAID1 only allow one disk removing. Which is more a RAID5 feature.The RAID-1 support in btrfs makes exactly two copies of each item of data, so you can lose at most one disk from the array safely. Lose any more, and you're likely to have lost data, as you've found out.quoted
I'm afraid Btrfs raid1 will not be working before the end of the world.It does work (as you demonstrated with the first disk being removed) -- but just not as you thought it should. Now, you can argue that "RAID-1" isn't a good name to use here, but there's no good name in RAID terminology to describe what we actually have here.
Technically, btrfs's "RAID1" implementation is much closer to RAID1E than traditional RAID1. See http://en.wikipedia.org/wiki/Non-standard_RAID_levels#RAID_1E or http://pic.dhe.ibm.com/infocenter/director/v5r2/index.jsp?topic=/serveraid_9.00/fqy0_craid1e.html Perhaps a new name, as with ZFS, might be appropriate. RAID-Z and RAID-Z2, for example, could not adequately be described by any existing RAID terminology and, technically, RAID-Z still isn't a RAID in the classical sense. -- Brendan Hide 083 448 3867 http://swiftspirit.co.za/