Today I got asked by a VMware admin at a customer how he could prevent or maybe schedule storage rescans.
He asked me this because he was adding 25 new datastores to 12 ESXi 5.1 hosts in a existing cluster and every time he added a datastore a rescan of the HBA adapters is automatically initated. As the cluster already was under a pretty heavy workload, the "rescan storm" started by his actions were having a impact on the performance on most of the VM's running in the cluster.
As far as I know it is not possible to schedule storage rescans, I don't see any added value to such a feature anyway.
But what is possible is disabling automatic host rescan of HBA adapters, this is done on a vCenter level with a advanced setting "config.vpxd.filter.hostRescanFilter" together with the value "False"
VMware has a KB article about this, so if you want to have a reference or want to know how to make this advanced setting from the webclient please have a look at KB1016873
One very important thing not to forget, change the value of the advanced setting to "True" as soon as you have finished adding the datastores !