So you've just created an additional LUN/volume and presented it to all your ESXi servers?

Now you want to rescan the HBAs on the servers so you can start using the storage, but you dont fancy manually doing this on say 10 or maybe even 100 servers.

Here is a very handy piece of VMware PowerCLI that will connect to your vCenter Server, get the list of clusters and hosts, then rescan all the HBAs on those hosts (ESX/ESXi). 

Note: Don't forget to change vcenter.domain.local to your vCenter server!!