6.7

Table Of Contents
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:
n
ESXi supports only local 4Kn SAS and SATA HDDs.
n
ESXi does not support 4Kn SSD and NVMe devices, or 4Kn devices as RDMs.
n
ESXi can boot only from a 4Kn device with UEFI.
n
You can use the 4Kn device to configure a coredump partition and coredump file.
n
Only the NMP plug-in can claim the 4Kn devices. You cannot use the HPP to claim these devices.
n
With vSAN, you can use only the 4Kn capacity HDDs for vSAN Hybrid Arrays. For information, see
the Administering VMware vSAN documentation.
n
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.
n
Workloads accessing the emulated 4Kn device directly using scatter-gather I/O (SGIO) must issue
I/Os compatible with the 512e disk.
Example: 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
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
Understanding Storage Device Naming
Each storage device, or LUN, is identified by several names.
vSphere Storage
VMware, Inc. 129