From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yuehai Xu Subject: Re: The huge different performance of sequential read between RAID0 and RAID5 Date: Thu, 28 Jan 2010 09:55:05 -0500 Message-ID: <100eff551001280655r2e173286nfca3dbf688609571@mail.gmail.com> References: <100eff551001271916y116de081la77982f4b5a03c73@mail.gmail.com> <20100128070606.GD3098@boogie.lpds.sztaki.hu> <100eff551001280631h7de01ba6n52d79fdfcea9445e@mail.gmail.com> <20100128144118.GB17369@twister.selfip.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <20100128144118.GB17369@twister.selfip.org> Sender: linux-raid-owner@vger.kernel.org To: Gabor Gombas Cc: linux-raid@vger.kernel.org, yhxu@wayne.edu List-Id: linux-raid.ids 2010/1/28 Gabor Gombas : > On Thu, Jan 28, 2010 at 09:31:23AM -0500, Yuehai Xu wrote: > >> >> md0 : active raid5 sdh1[7] sdg1[5] sdf1[4] sde1[3] sdd1[2] sdc1[1= ] sdb1[0] >> >> =A0 =A0 =A0 631353600 blocks level 5, 64k chunk, algorithm 2 [7/6= ] [UUUUUU_] > [...] > >> I don't think any of my drive fail because there is no "F" in my >> /proc/mdstat output > > It's not failed, it's simply missing. Either it was unavailable when = the > array was assembled, or you've explicitely created/assembled the arra= y > with a missing drive. I noticed that, thanks! Is it usual that at the beginning of each setup, there is one missing drive? > >> How do you know my RAID5 array has one drive missing? > > Look at the above output: there are just 6 of the 7 drives available, > and the underscore also means a missing drive. > >> I tried to setup RAID5 with 5 disks, 3 disks, after each setup, >> recovery has always been done. > > Of course. > >> However, if I format my md0 with such command: >> mkfs.ext3 -b 4096 -E stride=3D16 -E stripe-width=3D*** /dev/XXXX, th= e >> performance for RAID5 becomes usual, at about 200~300M/s. > > I suppose in that case you had all the disks present in the array. Yes, I did my test after the recovery, in that case, does the "missing drive" hurt the performance? Thanks! Yuehai > > Gabor > > -- > =A0 =A0 --------------------------------------------------------- > =A0 =A0 MTA SZTAKI Computer and Automation Research Institute > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0Hungarian Academy of Sciences > =A0 =A0 --------------------------------------------------------- > -- 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