ESXi supports storage devices with traditional and advanced sector formats. In storage, a sector is a subdivision of a track on a storage disk or device. Each sector stores a fixed amount of data.

This table introduces different storage device formats that ESXi supports.

Storage Device Format ESXi Software Emulation Logical Sector Size Physical Sector Size VMFS Datastore
512n N/A 512 512 VMFS5 and VMFS6 (default)
512e N/A 512 4096 VMFS5 and VMFS56 (default)
Note: Local 512e storage devices do not support VMFS5.
4Kn 512 4096 4096 VMFS6

512-Byte Native Format

ESXi supports traditional 512n storage devices that use a native 512-bytes sector size.

512-Byte Emulation Format

Due to the increasing demand for larger capacities, the storage industry has introduced advanced formats, such as 512-byte emulation, or 512e. 512e is the advanced format in which the physical sector size is 4096 bytes, but the logical sector emulates 512-bytes sector size. Storage devices that use the 512e format can support legacy applications and guest operating systems. These devices serve as an intermediate step to 4Kn sector drives.

4K Native Format with Software Emulation

Another advanced format that ESXi supports is the 4Kn sector technology. In the 4Kn devices, both physical and logical sectors are 4096 bytes (4 KiB) in length. The device does not have an emulation layer, but exposes its 4Kn physical sector size directly to ESXi.

ESXi detects and registers the 4Kn devices and automatically emulates them as 512e. The device is presented to upper layers in ESXi as 512e. But the guest operating systems always see it as a 512n device. You can continue using existing VMs with legacy guest OSes and applications on the host with the 4Kn devices.

When you use 4Kn devices, the following considerations apply:
  • ESXi supports only local 4Kn SAS and SATA HDDs.
  • ESXi does not support 4Kn SSD and NVMe devices, or 4Kn devices as RDMs.
  • ESXi can boot only from a 4Kn device with UEFI.
  • You can use the 4Kn device to configure a coredump partition and coredump file.
  • Only the NMP plug-in can claim the 4Kn devices. You cannot use the HPP to claim these devices.
  • With vSAN, you can use only the 4Kn capacity HDDs for vSAN Hybrid Arrays. For information, see the Administering VMware vSAN documentation.
  • Due to the software emulation layer, the performance of the 4Kn devices depends on the alignment of the I/Os. For best performance, run workloads that issue mostly 4K aligned I/Os.
  • Workloads accessing the emulated 4Kn device directly using scatter-gather I/O (SGIO) must issue I/Os compatible with the 512e disk.

Determine Device Format

To determine whether the device uses the 512n, 512e, or 4Kn format, run the following command.

esxcli storage core device capacity list

The following sample output shows the format type. 
Device                Physical Blocksize  Logical Blocksize  Logical Block Count         Size  Format Type
--------------------  ------------------  -----------------  -------------------  -----------  -----------
naa.5000xxxxxxxxx36f                 512                512           2344225968  1144641 MiB  512n
naa.5000xxxxxxxxx030                4096                512           3516328368  1716957 MiB  4Kn SWE
naa.5000xxxxxxxxx8df                 512                512           2344225968  1144641 MiB  512n
naa.5000xxxxxxxxx4f4                4096                512           3516328368  1716957 MiB  4Kn SWE