As specified in user manual, IOMeter shows only empty
physical drives, i.e. those that haven't any partitions.
So, if I have '/' on /dev/sda1, it only displays '/'
hiding sda1, but it still shows whole 'sda' as
available for write test and lets to run it without any
warnings. I guess it should at least warn users about
the data loss in this case, or may be better hide all
partitions that are substrings of the device names that
have partitions on them or at least known to be mounted.