On 29 October 2010 21:22, John Robinson <john.robinson@xxxxxxxxxxxxxxxx> wrote: > On 29/10/2010 15:18, Mathias BurÃn 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 the >> array continued where it left off before reboot. However, the >> performance was abysmal.. around 16MB/s compared to 70MB/s without the >> 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 > experimental implementation that doesn't work terribly well. If you're > 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] >> Â Â Â 5851054080 blocks super 1.2 level 5, 128k chunk, algorithm 2 >> [6/6] [UUUUUU] >> Â Â Â [===========>.........] Âreshape = 57.7% (1126387328/1950351360) >> finish=718.0min speed=19125K/sec >> >> unused devices:<none> >> >> 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 test >> 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 superblock > versions, but I don't know - I'm sorry that's not helpful. > > Cheers, > > John. > > Hi, Thanks for the answers. I got the speed up to around 36 MBps by disabling NCQ and changing some cache values, so there's only 36 minutes left or so now. I would love to help develop the multicore_raid456, but I'm not a coder. Patches welcome though! // Mathias -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
