vMMR collects data and provides visibility of performance statistics so you can determine if your application workload is regressed due to Memory Mode.
Intel Optane Persistent Memory can be configured in BIOS settings in App Direct or Memory Mode. In App Direct mode, persistent memory can be accessed as byte addressable, persistent memory along with DRAM. In Memory Mode, DRAM becomes the hardware cache and the larger PMem becomes volatile and appears as system memory.
Memory Mode is invisible and transparent to VMs. Once you configure the system in Memory Mode, the system appears as a traditional system with DRAM. A cluster can have a mix of hosts with different configurations. vSphere shows additional information about the system being in Memory Mode. ESXi programs performance counters that gather information about host level and VM level statistics. These performance statistics are used to create alarms. Statistics are also tracked in performance charts.
You can find out if the system is in Memory Mode in the host Summary tab, Memory Tiering: Hardware with some additional details.
You can also view the size of DRAM and PMEM under.
ESXi gathers and exposes two kinds of memory statistics:
- Host Level Statistics: A memory sub-component measures DRAM and PMem performance by programming performance counters. The host level statistics are total, read/write bandwidth, read/write latency and miss rate for the different memory types (DRAM, PMem).
- VM Level Statistics: vSphere monitors performance counters to get data on DRAM and PMEM read bandwidth of the VM.
Both Host and VM have new Memory pane under Performance charts. This shows memory details like Memory Utilization and Memory Reclamation along with new statistics. On the ESXi host level, you can monitor the Memory Bandwidth and Memory Miss Rate charts. On the VM level, you can view the PMem read bandwidth and DRAM read bandwidth. The advanced performance charts can be used to selectively plot any new statistics. For example, you can monitor the read/write latency and miss rate.
From the VMs tab of an ESXi host, you can view a list containing performance information about all virtual machines that reside on the host. To display information about the Memory Mode impact on a virtual machine, click the view columns () icon and select the Active Memory, DRAM Read Bandwidth, and PMem Read Bandwidth metrices.
There are two preconfigured default alarms, one at the host level (Host Memory Mode High Active DRAM Usage) and another at the VM level (Virtual Machine High PMem Bandwidth Usage). If the alarm condition is met, an event will be published to trigger the corresponding alarm. You can also create custom alarms based on performance metrics. vMMR alarms only work on hosts configured with Memory Mode.
When DRS is enabled and fully automated in the cluster, if the active memory utilization of the host is above certain percentage of the size of the DRAM cache, DRS might move some VMs out of the host in order to balance the load.
For more information, see vSphere Monitoring and Performance.