N-way mirror read speedup in zfsonlinux

[Alexander Motin]

On 14.08.2013 16:50, Steven Hartland wrote:
> So based on mav's comments I've created a new version of the load balanced
> patch which takes into account the last IO's locality on the disk.

I like it. Thank you!

Just a few comments:
1) I guess your change to scsi_da.c will send "GEOM::rotating" attribute 
change every time disk is probed (including each open) even when nothing 
really changed. It is not fatal, but absolutely unneeded overhead.
2) You are always giving full locality bonus to SSDs. It means that HDDs 
quite likely won't be used even for sequential read operations until 
SSDs are really busy, while that is the only point where HDDs still 
could if not compete but at least be useful. Surely it very much depend 
on specific devices characteristics, but I would try to give SSD half 
(or may be 3/4), so that precisely positioned HDD could still do 
something it can.
3) bde@ would argue about too long sysctl comments, while for me at 
least first is quite tangled.
4) I don't very like idea of expanding struct disk every time 
(especially not at the end). While that is probably easier then 
alternatives, now we have d_getattr method specifically to avoid that.

-- 
Alexander Motin