From mboxrd@z Thu Jan 1 00:00:00 1970 From: hank peng Subject: Re: about raid5 recovery when created Date: Tue, 8 Dec 2009 21:52:14 +0800 Message-ID: <389deec70912080552r363e6412j9b10ebed5481ebeb@mail.gmail.com> References: <389deec70912080501u6c6bc90ei2d34ef245a1dae9e@mail.gmail.com> <20091208131446.GA21130@cthulhu.home.robinhill.me.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20091208131446.GA21130@cthulhu.home.robinhill.me.uk> Sender: linux-raid-owner@vger.kernel.org To: linux-raid List-Id: linux-raid.ids 2009/12/8 Robin Hill : > On Tue Dec 08, 2009 at 09:01:23PM +0800, hank peng wrote: > >> Hi, all: >> As we know, when a raid5 array is created, recovery will be going on >> which involves some read, one xor and one write. Since there is no >> real data in the disk at the time, besides, if I am willing to wait >> for recovery to complete and then use this raid5, how about adding >> support for a fast recovery method? Right now, what is in my mind is >> zero all disks which belong to this raid5. I think it will increase >> raid5 recovery speed when created and decrease CPU usage, since all >> zero is also XORed. >> What do raid developers think? >> > It'll decrease CPU usage but increase I/O - you're now needing to wri= te > to all disks. =C2=A0Most systems will be I/O limited rather than CPU = limited, My CPU is an embedded arch, 1.3GHz, single core, so CPU usage is import= ant. In low-end NAS box, I think, this requirment is normal. > so the current approach works better. =C2=A0If you want to zero the d= isks > then do this before creating the array - you can then use --assume-cl= ean > to skip the resync process. > > Cheers, > =C2=A0 =C2=A0Robin > -- > =C2=A0 =C2=A0 ___ > =C2=A0 =C2=A0( ' } =C2=A0 =C2=A0 | =C2=A0 =C2=A0 =C2=A0 Robin Hill =C2= =A0 =C2=A0 =C2=A0 =C2=A0 | > =C2=A0 / / ) =C2=A0 =C2=A0 =C2=A0| Little Jim says .... =C2=A0 =C2=A0= =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 = =C2=A0 =C2=A0| > =C2=A0// !! =C2=A0 =C2=A0 =C2=A0 | =C2=A0 =C2=A0 =C2=A0"He fallen in = de water !!" =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 | > --=20 The simplest is not all best but the best is surely the simplest! -- To unsubscribe from this list: send the line "unsubscribe linux-raid" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html