Effects of setting linux block device readahead size

Hi all,

I've started to display the effects of changing the Linux block device
readahead buffer to the sequential read performance using fio.  There
are lots of raw data buried in the page, but this is what I've
distilled thus far.  Please have a look and let me know what you
think:

http://wiki.postgresql.org/wiki/HP_ProLiant_DL380_G5_Tuning_Guide#Readahead_Buffer_Size

Regards,
Mark