In kernels 2.6.27-rc1 and rc2 /proc/diskstats only displays 15 scsi devices
(includes partitions), or 9 actual devices (sda-i). I'm using multipath and
device mapper, none of the dm devices are in the list either. The 2.6.26
kernel lists all devices, including all dm devices. Since diskstats does
not contain all the disks, iostat will not display the io for the disks that
are missing, which means, I can't see all of the io activity that is taking
place on the system. This seems like a bug to me.
Andy