* does this work already? (i cant experiment yet, disks are on purchase * list i have to get signed before i get the disks)

You mean mirroring? Yes it's working, has been for a few months.

* and am i right assuming (some old post listed these) that 128 is the * interleave value that gives me most speed for reads?

Depends on what kind of reads you are talking about. For large sequential reads (here the size of individual read()s don't matter -- the "large" refers to the total size that's read in succession) and many disks, something a little smaller is usually better, e.g., 32 or 64.

For random reads, it should probably be the size of the read, i.e., if your reads are 16K, then 32 would do the best. (Unless the read sizes are very large, say 1M or so...in which case, treat this as "sequential" as described above.) Of course, I'm assuming the reads occur at offsets that are integer multiples of the read sizes -- if not, I guess you want something a little larger to reduce the chance of a single read falling between two disks.

However, since 128 does reasonably well for both reads and writes, that is the size I would recommend for normal (read/write) workloads.