Another important question to ask: what are you doing with what you learned from the test? Nagios? Snmptrap? Zabbix? Grapha? Statd ? Email notification? Smoke signals?
I wrote a nagios check once called check_rofs which would write a file read it then delete it and report how that went. Nagios handled telling the right person via the correct means and graphing performance data ( like time to write, time to read, time to unlink.)
A system like this has the downside of not checking often enough for some i.e. every 5min by default. I suspect that would be fine for your needs.