ESXi supports iSCSI technology that enables a host to use an IP network to access remote storage. With shared networked storage in vSphere you can aggregate storage resources to be more flexible when provisioning the resources to virtual machines.

In this scenario, you are the system administrator of a small vSphere environment. You have an iSCSI storage device in your network and want to use it with your ESXi hosts. You can use software iSCSI adapter included in ESXi to establish a connection to iSCSI storage and make it available for use in your environment. The iSCSI device has raw partitions, which you can format and add as datastores to your inventory.

iSCSI shared storage might be an enterprise-level hardware system or a software solution using commodity hardware.

Without access to shared storage, the virtual machines on a host are limited to the host's physical hard disk to contain the virtual machines' virtual disks. If you have centralized and aggregated storage resources, it releases virtual machines from depending on local storage. Multiple hosts can access datastores on networked storage concurrently.

Workflows for Adding iSCSI Storage
iSCSI workflows

For information about the storage options in vSphere, see the vSphere Storage documentation.