Comment 2 for bug 802331

Evidence of only reading from one half, from iostat -x:

Device: rrqm/s wrqm/s r/s w/s rkB/s wkB/s avgrq-sz avgqu-sz await r_await w_await svctm %util
sdd 1071.40 106.80 283.80 13.40 5421.60 480.00 39.71 1.40 4.72 4.05 19.10 2.12 63.00
sde 0.00 106.80 0.00 13.20 0.00 479.20 72.61 0.16 11.82 0.00 11.82 2.27 3.00
sdf 1111.00 107.00 287.80 13.40 5594.40 480.80 40.34 0.98 3.25 2.82 12.39 1.77 53.40
sdg 0.00 106.60 0.00 13.80 0.00 480.80 69.68 0.12 8.41 0.00 8.41 3.91 5.40