From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roberto Spadim Subject: Re: mdadm raid1 read performance Date: Wed, 4 May 2011 21:24:06 -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 2011/5/4 Liam Kurmos : > Thanks guys! > > > >>> raid10: 220MB/s >> >> Assuming the default 'n2' layout, I would expect 2*140 or 280, so th= is 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 re= ad-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 and >>> use rsync to keep constant back up. >> >> If you have somewhere to rsync to, then you have more disks so RAID1= 0 might >> be an answer... but I suspect you cannot move disks around that free= ly :-) >> > > no need now! f2 layout is awesome. hum, you should consider you application..... for example, if you need a big ALTER TABLE (SQL database), that must be very fast to don=B4t stop your production server, you should use f2 or raid0 ehehehe but if you have a stable application that you need multiuser acess, raid1 or n2 layout could be better backup i=B4m running with raid10 f2, or raid1+raid0, and production machine i=B4m using raid1 and linear to get more space don=B4t forget to align partitions if you use it > > 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