Hi.
i think that starting to measure the uptime can come and bite you back.
high uptime can be actually showing a bad service, rather good (no known issue mitigation. no security patching, no perf improvements, no full support).
i can suggest the following measurements:
Amount of P1/P2 cases
AVG Length of case being open in active status
System performance breach
You can ask the netapp account rep of partner for the data (i coulden't extract it from the support site).
Gidi