Giving top priority to a rebuild instead of serving userland?
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
Signature · 2 lines
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Martin Cracauer <[email protected]> http://www.cons.org/cracauer/
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.
Alex.
Quoted 16 lines · Martin Cracauer
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_wrtncontiguously. 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 :-)
Quoted 8 lines
Martin
-- %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Martin Cracauer <[email protected]> http://www.cons.org/cracauer/
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Alexander Lyakas wrote on Mon, Jan 09, 2012 at 10:40:49PM +0200:
Quoted 8 lines
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
Quoted 5 lines
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?
Martin
Quoted 28 lines
Alex.
Quoted 24 lines · Martin Cracauer
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_wrtncontiguously. ?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 <[email protected]> ? http://www.cons.org/cracauer/
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [email protected]
More majordomo info at ?http://vger.kernel.org/majordomo-info.html
Signature · 2 lines
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Martin Cracauer <[email protected]> http://www.cons.org/cracauer/
Quoted 15 lines · Martin Cracauer
Alexander Lyakas wrote on Mon, Jan 09, 2012 at 10:40:49PM +0200:
Quoted 8 lines
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_maxQuoted 5 lines
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.
Quoted 4 lines
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 :)
Quoted 31 lines
Martin
Quoted 28 lines
Alex.
Quoted 24 lines · Martin Cracauer
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_wrtncontiguously. ?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 <[email protected]> ? http://www.cons.org/cracauer/
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to [email protected]
More majordomo info at ?http://vger.kernel.org/majordomo-info.html
Signature · 1 line
Anssi Hannula