Memory Tiering in VCF 9 allows ESXi hosts to use a second, lower-cost memory tier—such as NVMe SSDs alongside traditional DRAM. vSphere intelligently manages these tiers by placing frequently accessed (“hot”) data in DRAM and moving less frequently accessed (“cold”) data to the secondary tier.
Advantages:
Higher effective memory capacity per host without requiring large DRAM investments
Improved VM density while maintaining near-DRAM performance
Automatic tiering and memory placement managed by vSphere, with no changes required inside guest VMs
The ESX host uses PCIe-based NVMe devices as a secondary layer of memory, this results in overall increase of the ESX host memory.
Key Pointers:
- Tiered Memory is utilized exclusively for the memory of running virtual machines and not for the ESX kernel or system services.
- Virtual machines that require high performance and low latency do not make use of tiered memory.
- Memory tiering is enabled through an advanced configuration setting. This feature can be activated at the cluster level using Configuration Profiles or individually on each ESX host.
- You can assign the required NVMe device through the command line:
esxcli system tierdevice create -d /vmfs/devices/disks/xxxxxxx
esxcli system tierdevice list - You can verify that memory tiering is configured by navigating to:
ESX Host → Configuration → Hardware → Overview
Requirements:
- vCenter 9.0 or later
- ESX 9.0 or later
- Supported NVMe device
Reference link: https://techdocs.broadcom.com/us/en/vmware-cis/vsphere/vsphere/9-0/how-do-i-activate-memory-tiering-in-vsphere-.html