VMware Storage I/O Control is alerting me of the following:
external I/O workload has been detected on shared datastore running Storage I/O Control (SIOC) for congestion management
This is because VMware Storage I/O Control uses its historical data to predict that there is an external (a server or something else) running on the datastore. This can be a big problem because Storage I/O Control will be throttling access to the datastore from VMware (that it has control of), which will be incorrect because it cannot factor the external I/O workload. This will cause VMs to run slowly.
Possible causes of the External I/O workload has been detected on shared datastore alert can be:
You haven’t enabled Storage I/O Control on all VMware datastores
You have setup another server to use the same volume
You have a problem with your SAN, causing Storage I/O Control’s historic data to be different
You have changed your SAN’s architecture, resulting in the same effect as above