From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Robinson Subject: Re: mdadm / RAID, a few questions Date: Fri, 29 Oct 2010 21:22:13 +0100 Message-ID: <4CCB2CF5.9010402@anonymous.org.uk> References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: =?UTF-8?B?TWF0aGlhcyBCdXLDqW4=?= Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On 29/10/2010 15:18, Mathias Bur=C3=A9n wrote: > Hi, > > I've a few questions in relation to mdadm and performance. System > details follow below: > > Intel Atom 330 @ 1.6Ghz (dualcore, HT), 4GB RAM [...] > Question 1: I saw that in Linux 2.6.36 (perhaps earlier versions as > well) you have the kernel config option CONFIG_MULTICORE_RAID456. I > tried enabling it, booted to 2.6.36 from 2.6.35, and rebuilding of th= e > array continued where it left off before reboot. However, the > performance was abysmal.. around 16MB/s compared to 70MB/s without th= e > option turned on. Is this a bug, or is it because the Atom has no > grunt to speak of? No, the performance of MULTICORE_RAID456 is abysmal on any CPU. It's an= =20 experimental implementation that doesn't work terribly well. If you're=20 interested in developing, by all means help, but if not, turn it off. > Question 2: The array is now recovering since I've grown it to 6 from= 4 devices: > $ cat /proc/mdstat > Personalities : [raid6] [raid5] [raid4] > md0 : active raid5 sdf1[0] sde1[5] sdg1[6] sdc1[3] sdd1[4] sdb1[1] > 5851054080 blocks super 1.2 level 5, 128k chunk, algorithm 2 > [6/6] [UUUUUU] > [=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D>.........] reshape =3D 57.= 7% (1126387328/1950351360) > finish=3D718.0min speed=3D19125K/sec > > unused devices: > > Is there a way to speed it up? /proc/sys/dev/raid/speed_limit_min is > 100000 (100k), /proc/sys/dev/raid/speed_limit_max is 1000000 (1000k). No, that's probably about right on something as weak as an Atom. Let it= run. > Question 3: Before I created this RAID5 array I did a quick RAID0 tes= t > array just for fun, using 2 full devices (not partitions). Now I have > this: [...] Sorry, I don't know the answer to this. I suspect it's to do with=20 superblock versions, but I don't know - I'm sorry that's not helpful. Cheers, John. -- 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