PowerEdge: How to Configure PERC H965 and Newer Controllers for ESXi 9 4Kn End‑to‑End

Applies to:

• Dell PowerEdge servers with PERC12/PERC13 (example: PERC H965/H975)
• VMware vSphere/ESXi 9.0

Definitions (quick reference):

• 512n: 512‑byte logical sector and 512‑byte physical sector
• 512e: 512‑byte logical sector with 4096‑byte physical sectors (emulation at the device level)
• 4Kn: 4096‑byte logical sector and 4096‑byte physical sector (native 4K)
• 4Kn SWE: ESXi identifies the device as 4Kn but uses a software emulation path (reported as "4Kn SWE" in ESXi output)
• 4Kn E2E: Virtual machine (VM) uses a 4Kn Virtual Machine Disk (VMDK) on a 4Kn backing device, avoiding 512‑byte emulation. VMs can understand a 4Kn backend and issue 4K I/O through a 4Kn virtual disk starting with vSphere 9.0.

PERC12+ default virtual disk sector size:

With PERC12 (H965) and later controller families, all virtual disks are created by default as 4Kn regardless of the physical disk sector format (512e, 512n, or 4Kn).

Example:
If a PERC H965 virtual disk is created using physical disks that are 512e, 512n, or 4Kn, the virtual disk is still presented as 4Kn to the operating system.

Important: PERC12+ controllers cannot create 512n virtual disks.

Older controller behavior (PERC10/PERC11):

Older generations (for example PERC11 H755 and PERC10 H745/H740) typically created virtual disks based on the sector size of the member physical disks:

• If member disks were 512e/512n, the virtual disk sector size was 512B
• If member disks were 4Kn, the virtual disk sector size was 4Kn

ESXi 4Kn Support: What Changed in ESXi 9:

VMware introduced support for 4Kn devices in ESXi 6.7, but prior to ESXi 9 this support was not end-to-end. In those earlier versions, a VM created on a 4Kn device typically used a 512B emulated virtual disk layered on top of the underlying 4Kn device

With ESXi 9, VMware adds true 4Kn end-to-end (E2E) support, allowing VMs to reside on 4Kn VMDKs without requiring 512B software emulation.

Requirements for 4Kn End-to-End (E2E):

ESXi/vSphere requirements:

To create and run VMs with 4Kn E2E, the following must be true:

• ESXi 9 host
• VM hardware version 21 or later
• PERC driver version 8.11 or later
• Storage devices are NVMe and or SSD
  • Spinning hard drives are not supported for ESXi 9 4Kn E2E in this scenario
• vCenter 9 or the ability to use vmkfstools
• An older ESXi version must not have previously claimed the virtual disk/datastore.
• The Virtual Machine OS or Appliance must support installation on a 4k device. 

Why 4Kn End-to-End Alignment Matters (Performance Impact):

If the workload issues 4K I/O (common for databases and many modern file systems), 4Kn E2E alignment avoids ESXi kernel translation overhead.

Example impact scenario:

When running a 50GB FIO 4K write test inside a VM,

• If the VM is on a 4Kn device using 512B software emulation, ESXi must translate 4K writes into 512B-sector semantics in real time.
• This translation can increase kernel latency (for example, Kernel Average (KAVG) spikes in ESXTOP), sometimes reporting sustained latency far above expected values, +1000ms.
• The storage device itself may be healthy; the observed penalty is often at the ESXi kernel translation layer, resulting in IOPS/throughput below expected performance.

This can be worsened if the VM has snapshots present, because additional overhead and translation are introduced for snapshots.
 

Examples and commands that can be run to confirm if a virtual disk is valid for 4kn E2E support.

Figure 1: A Virtual Disk created on a PERC H965i with NVMe drives running firmware version 8.14. The disk is identified as Disk (SSD), which is a requirement for 4k E2E support.

Figure 2: Using esxcli command "esxcli storage core device capacity list" displays Physical and Logical block sizes and the Format type which must be 4k to support E2E.

In the below example, there is one NVMe drive in Passthrough Mode reported as 512n and three PERC virtual disks reported as 4k. 
 

Figure 3: Using esxcli command "esxcli storage core device capacity list" displays Physical and Logical block sizes and the Format type which must be 4k to support E2E.

In the below example, the Virtual Disk was created on a PERC H965i controller using a firmware version older than the 8.11+ and or was previously claimed by an ESXi version less than ESXi9 with hardware version 21 or driver version less than 8.11. The Format Type is reported as "4kn SWE" and the Logical block size is Software Emulated to 512b. This device does not meet the requirement's for 4k E2E.
 

Figure 4: vCenter 9, selecting the sector size in the Virtual Hardware UI during VM creation
 

For more information related to Sector Formats for Storage Devices in ESXi 9, see Broadcom article Sector Formats for Storage Devices (External Link)