Added by default during VM creation, the storage controller is used to access virtual disks, CD/DVD devices, and SCSI devices. Storage controllers are presented to VMs as different types of storage controllers—BusLogic Parallel, LSI Logic Parallel, LSI Logic SAS, VMware Paravirtual SCSI, AHCI, SATA, and NVMe, as described in Chapter 7, Advanced Storage Management.

Generally, the default controller optimized for best performance is assigned to the VM based on the guest OS selection, device type, and VM compatibility. A maximum of four SATA, four SCSI, and four NVMe controllers are supported for each VM. If during the VM creation, the Windows Server 2008 or 2012 guest OS is selected, for example, the LSI Logic SAS controller is assigned by the system.

When a VM is created, two storage controllers are assigned by default:

• SATA: This controller is assigned to access CD/DVD devices and supports up to 30 devices. If you have multiple disks, to distribute the load and improve performance, you can add up to four controllers per VM. An AHCI SATA controller is supported for VMs with ESXi 5.5 and later compatibility. A SATA controller is supported by most guest OS and is assigned by default to CD/DVD devices.
• SCSI: Depending on the guest OS, many VMs have this controller configured by default. A single controller supports up to 15 devices. If you have multiple disks, to distribute the load and improve performance, you can add up to four controllers per VM. In the new SCSI controller, you can enable SCSI bus sharing to allow the virtual disk to be shared by the VM, for example, for building a guest cluster. There are three possible options available:

None: Virtual disk cannot be shared
Physical: Virtual disk can be shared by VM on the same host
Virtual: Virtual disk can be shared by VM on any host