iSCSI is believed to be both cost effective and easier to use than fibre. The storage protocol has some potential unknowns that need to be worked around or avoided. Storage on its own network makes it easier to diagnose problems with either network or network. iSCSCSI storage environments are still 1GBE based, even newer ones. For some, especially smaller environments, 1GE is all the storage I/O they will ever need most of the time. For others they will look at using multiple 1GAs connections from the servers to increase performance or 10GE.”]
Source: https://www.darkreading.com/database-security/the-truth-about-iscsi