The use of disk shares will work just fine as long as the datastore is seen by a single ESXi host. Unfortunately, that is not a common case. Datastores are often shared among multiple ESXi hosts. When datastores are shared, you bring more than one localhost scheduler into the process of balancing the I/O among the VMs. However, these lost host schedulers cannot talk to each other and their visibility is limited to the ESXi hosts they are running on. This easily contributes to a serious problem called the noisy neighbor situation.
In the following example, since VM-C is the only VM on ESX-02, it gets to consume the entire queue depth, which could starve VMs on the other two hosts. If VM-C does indeed do a lot of I/O consuming of the LUN's queue depth, then it will be referred to as a noisy neighbor:
The job of SIOC is to enable some form of communication between...