raw filesystem counters

[E.S. Rosenberg]

Hi,
Hopefully I'm not asking something that has been answered thousands of
times, I did search but did not find.

Is there any way to access raw disk counters similar to those found on
Linux in:
/sys/class/block/<device>/stat

Preferably also by accessing such a virtual file and not by using iostat /
zpool iostat which are already pre-processing counters and need to be run
constantly to get accurate real-time estimates.

So far I have not stumbled upon the right sysctl key to get these counters
(and TBH as said before I'd much rather read a "file" then run a command
though that matters less as long as the counters are raw).

Background: I'm trying to get a better idea of what is going on with our
IO, I would like to push the counters into Zabbix and maybe other data
analysis software later so I prefer raw counters that can then be processed
by whatever software we are using.

Thanks!
Eli