We are running multiple netapp storage filers at two independent datacenters with an network latency of 300ms between the datacenters. Should we run two independend OCUM instances, one per datacenter or does it work to have just one instance of OCUM and connect the "remote filers" via WAN link? How would it impact the OCUM performance?
There are a lot of factors that govern the monitoring of multi site Netapp gears from a single Unified Manager instance. There will be ~100 health ZAPIs fired every 15 mins ( during each polling cycle). And you have already mentioned the latency is around 300ms between the sites. Looking at all these factors it is advisable to have a seperate instance of Unified Manager per site.
I would also encourage you to read through the Best Practices TR here. Hope this helps you in planning your UM 7.2 instance deployment.