Improving geom_mirror(4)'s read balancing

[Ivan Voras]

Maxim Sobolev wrote:

> The patch is available here:
> http://sobomax.sippysoft.com/~sobomax/geom_mirror.diff. I would like to
> get input on the functionality/code itself, as well on what is the best
> way to add this functionality. Right now, it's part of the round-robin
> balancing code. Technically, it could be added as a separate new
> balancing method, but for the reasons outlined above I really doubt
> having "pure" round-robin has any practical value now. The only case
> where previous behavior might be beneficial is with solid-state/RAM
> disks where there is virtually no seek time, so that by reading close
> sectors from two separate disks one could actually get a better speed.
> At the very least, the new method should become default, while "old
> round-robin" be another option with clearly documented shortcomings. I
> would really like to hear what people think about that.

Have you perhaps seen this:

http://www.freebsd.org/cgi/query-pr.cgi?pr=kern/113885

I'm using the patch in the PR and it helps a bit, similar to what you
have seen. Pawel is silent about the issue so I guess it can also be
taken as silent approval :)


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