From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Brown Subject: Re: about raid5 recovery when created Date: Thu, 10 Dec 2009 12:43:59 +1100 Message-ID: <20091210124359.4dd1a93a@notabene.brown> References: <389deec70912080501u6c6bc90ei2d34ef245a1dae9e@mail.gmail.com> <20091208131446.GA21130@cthulhu.home.robinhill.me.uk> <389deec70912080549h1b22489es612235ad29354d6b@mail.gmail.com> <20091208135600.GB21130@cthulhu.home.robinhill.me.uk> <389deec70912080603w47d7fda3jf021af169ac1c48c@mail.gmail.com> <4877c76c0912090030r266337afs394ecec463555258@mail.gmail.com> <389deec70912090329w65b7fa06hff8b75ad8f637307@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <389deec70912090329w65b7fa06hff8b75ad8f637307@mail.gmail.com> Sender: linux-raid-owner@vger.kernel.org To: hank peng Cc: Michael Evans , linux-raid List-Id: linux-raid.ids On Wed, 9 Dec 2009 19:29:04 +0800 hank peng wrote: > I think it is better to implement this function in kernel's md layer. > I wonder what Neil Brown think of this? I don't think it is worth the effort. You probably would save some CPU time as you don't need to XOR, but as has been said, we are usually IO bound, not CPU bound. With the current arrangement, you can start using the array immediately - you don't have to wait for the initial recovery to complete. If you zeroed all devices at create time, you would have to wait for that to complete before using the array. So I see very little gain, and significant cost. NeilBrown