From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: mdadm raid1 read performance Date: Wed, 4 May 2011 21:25:55 -0300 Message-ID: References: <20110504105822.21e23bc3@notabene.brown> <4DC0F2B6.9050708@fnarfbargle.com> <20110505094538.0cef02cc@notabene.brown> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Liam Kurmos Cc: NeilBrown , Brad Campbell , Drew , linux-raid@vger.kernel.org List-Id: linux-raid.ids raid10,f2 is a stripe configuration and mirror too, think about it like= this: disk 1,2,3,4 /dev/md0 =3D raid1 (1,2) /dev/md1 =3D raid1 (3,4) /dev/md2 =3D raid0 (stripe) (md0,md1) <--- it=B4s near raid10 2011/5/4 Liam Kurmos : > incidentally what does the f2 layout do that it performs so much > better than the default? > > Liam > > > On Thu, May 5, 2011 at 1:14 AM, Liam Kurmos = wrote: >> Thanks guys! >> >> >> >>>> raid10: 220MB/s >>> >>> Assuming the default 'n2' layout, I would expect 2*140 or 280, so t= his is a >>> little slow. =A0Try "--layout=3Df2" and see what you get (should be= more like >>> RAID0). >> >> >> mdadm -C /dev/md0 --level=3Draid10 --layout=3Df2 --raid-devices=3D4 >> /dev/sda1 /dev/sdc1 /dev/sdd1 /dev/sde1 >> >> dd if=3D/dev/md0 of=3D/dev/null bs=3D1M count=3D1000 >> 1000+0 records in >> 1000+0 records out >> 1048576000 bytes (1.0 GB) copied, 2.23352 s, 469 MB/s >> >> :D >> >> awesome!! >> >>> >>>> raid5: ~165MB/s >>> >>> I would expect 3*140 or 420, so this is very slow. =A0I wonder if r= ead-ahead is >>> set badly. >> >>> Can you: >>> =A0 blockdev --getra /dev/md0 >>> multiply the number it gives you by 8 and give it back with >>> =A0 blockdev --setra NUMBER /dev/md0 >>> >> >> genius. >> >> im not really sure what this did but it totally fixed the problem. >> >> look ahead was 768, set it 6144 and immediately got 400MB/s >>> >>>> raid1: ~140MB/s =A0(single disk speed) >>> >>> as expected. >>> >>>> >>>> for 4 disks raid0 seems like suicide, but for my system drive the >>>> speed advantage is so great im tempted to try it anyway and try an= d >>>> use rsync to keep constant back up. >>> >>> If you have somewhere to rsync to, then you have more disks so RAID= 10 might >>> be an answer... but I suspect you cannot move disks around that fre= ely :-) >>> >> >> no need now! f2 layout is awesome. >> >> many thanks, >> >> Liam >> >> >> >>> NeilBrown >>> >>> >>> >>>> >>>> cheers for you responses, >>>> >>>> Liam >>> >> > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid"= in > the body of a message to majordomo@vger.kernel.org > More majordomo info at =A0http://vger.kernel.org/majordomo-info.html > --=20 Roberto Spadim Spadim Technology / SPAEmpresarial -- 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