N-way mirror read speedup in zfsonlinux

[Will Andrews]

On Fri, Jul 12, 2013 at 3:21 AM, Martin Matuška <martin at matuska.org> wrote:
> zfsonlinux has implemented a change in the N-way mirror device selection
> algorithm by selecting the device with the least pending I/O instead of
> random selection. They measured an increased read bandwidth increase up to
> 50% and IOPS increase up to 10%.
>
> this might be useful for common ZFS code and we might consider porting this
> to illumos and FreeBSD:
> https://github.com/zfsonlinux/zfs/issues/1461
> https://github.com/zfsonlinux/zfs/commit/556011dbec2d10579819078559a77630fc559112

Just a general comment: This is a well-documented improvement, much
better than many I've seen.  Not only was the research process
documented, but so was much of the change itself.  I think we would
all benefit if all other ZFS changes had this level of documentation.

--Will.