>>>>> "Neil" == NeilBrown <neilb@xxxxxxx> writes:
>> + blk_queue_io_opt(mddev->queue, chunk_size * (mddev->raid_disks >>
>> blk_queue_io_opt(mddev->1));
Neil> ">> 1" is wrong. A raid10 may have more than 2 copies for each
Neil> block.
I recall pondering when I wrote that. Never got around to revisiting
the issue. Your RAID10 implementation is a bit hipper than most :)
Neil> This calculation needs to be a bit more subtle and take about of
Neil> the particular layout (near, offset, or far).
Why would layout interfere with preferred I/O size?
How about:
if (conf->raid_disks % conf->copies)
blk_queue_io_opt(mddev->queue, chunk_size * conf->raid_disks);
else
blk_queue_io_opt(mddev->queue, chunk_size *
(conf->raid_disks / conf->copies));
I.e.:
2 drives, 2 copies: a1 a1 optimal I/O = 1 * chunk_size
3 drives, 2 copies: a1 a1 a2
a2 a3 a3 optimal I/O = 3 * chunk_size
4 drives, 2 copies: a1 a1 a2 a2 optimal I/O = 2 * chunk_size
4 drives, 3 copies: a1 a1 a1 a2
a2 a2 a3 a3
a3 a4 a4 a4 optimal I/O = 4 * chunk_size
And so on. Does that make sense? I.e. we try to keep all drives
equally busy.
Neil> You seem to be treating raid4 like raid6 :-)
Whoops. I always forget about raid4. Fixed.
--
Martin K. Petersen Oracle Linux Engineering
--
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
