On 09.01.2012 23:57, Martin Cracauer wrote: > Alexander Lyakas wrote on Mon, Jan 09, 2012 at 10:40:49PM +0200: >> Hi, >> >> Have you tried to play with: >> /proc/sys/dev/raid/speed_limit_max >> /proc/sys/dev/raid/speed_limit_min >> /sys/block/mdXXX/md/sync_speed_min >> /sys/block/mdXXX/md/sync_speed_max >> >> For me these work very well. You can also set min > max, in which case >> max is totally ignored. >> According to the kernel code, md keeps submitting sync requests until >> it reaches the minimum speed, and then it checks the "userland" IO and >> the high speed limit. > > Looks like what I need. Thanks so much. > > These two sets are identical in functionality (other than one being > per-set), right? Yes. I also often set minimum sync speed for the same reasons as you (i.e. there is light-to-moderate unimportant userspace I/O going on which slows down reshape/rebuild considerably), however, at least in the past I could stall the userspace processes (almost?) completely by setting a too high minimum sync speed, so I had to leave some significant margin for userspace I/O and speed fluctuation. It'd be nice if md could handle the kind of prioritizing you describe itself dynamically (if it is reasonably possible, that is), but I guess that would be very low-priority feature request as changing the min sync speed usually suffices :) > Martin > >> Alex. >> >> >> On Mon, Jan 9, 2012 at 4:21 PM, Martin Cracauer <cracauer@xxxxxxxx> wrote: >>> I am doing a resize on a 4 x 1 TB raid5 array (going to 5x 1 TB). >>> >>> When there is no userland I/O it reports about 1000 minutes to >>> rebuild. ?However, minor amount of userland demand makes it shoot up >>> to 3500-4000 as the rebuild puts it's own interests behind. >>> >>> However, the I/O there is garbage, in this case a disk-noisy web >>> browser. ?Can I tell md to give priority to it's rebuild and serve >>> userland as it pleases with -say- a maximum of 10% rebuild time >>> increase? Yes I know that'll make the system very sluggy. >>> >>> I would be finished already but overnight I left a browser tab open >>> that caused according to iostat 400-500 Blk_wrtn contiguously. ?That >>> is when *not* actually using the browser (I'll report that as a bug). >>> Now I am still at 38% rebuild. ?Didn't seem worth the price I payed :-) >>> >>> Martin >>> -- >>> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% >>> Martin Cracauer <cracauer@xxxxxxxx> ? http://www.cons.org/cracauer/ >>> -- >>> 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 > -- Anssi Hannula -- 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
