Hello,
Yes, if you mount two datastores using two different IP addresses, you'll only use two links from the ESXi hosts to the switch. If you only use two links from a controller, then you'll use both links on the way back. Don't forget that each device in the path (the ESXi host, the switch, and the controller) will use its own hash algorithm to determine on which uplink or port to send traffic.
This is a fine design, even if you only use two datastores to begin with. If you're intent on using all four links at the start, then look at how you use your datastores. Are you breaking up .vmdks by OS and data? Are you breaking out VM page files and ESXi host .vswp files? Perhaps you should. Are you replicating between sites? If so, you may want separate datastores for those transient data types. This way, you can create a few more datastores and spread out the bandwidth.
All the best,
Mike
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Message was edited by: Mike Brown for grammar