Every VM must have the XenServer Tools (Management Agent) installed. Without them, the hypervisor cannot see inside the VM. You will get inaccurate memory readings and zero I/O metrics. A VM without tools is essentially a "black box."
For more advanced visualization or cross-platform management, several enterprise tools integrate with XenServer: What monitoring capabilities would you like in XenServer? xenserver monitoring
XenServer monitoring is the process of tracking the performance, health, and availability of a Citrix Hypervisor (formerly XenServer) environment to ensure peak efficiency of virtualized workloads. Effective monitoring focuses on resource utilization across the physical host and its guest virtual machines (VMs). Critical XenServer Metrics to Track Every VM must have the XenServer Tools (Management
: Track free memory on the host and the amount of memory ballooned or swapped by VMs. XenServer's Dynamic Memory Control (DMC) should be monitored to ensure VMs have enough RAM to function without hitting performance bottlenecks. A VM without tools is essentially a "black box
The "Health Check" feature, which integrates with Citrix Insight Services to identify configuration issues. 2. RRDtool and XenServer API