CPU Performance Analysis Flashcards
Host: CPU usage is consistently high.
Virtual machine: CPU usage is above 90%. CPU ready is above 20%. Application performance is poor.
Likely Causes?
The host has insufficient CPU resources to meet the demand.
Too many virtual CPUs are running on the host.
Storage or network operations are placing the CPU in a wait state.
The guest OS generates too much load for the CPU.
Host: CPU usage is consistently high.
Virtual machine: CPU usage is above 90%. CPU ready is above 20%. Application performance is poor.
Potential Solutions?
Add the host to a DRS cluster.
Increase the number of hosts in the DRS cluster.
Migrate one or more virtual machines to other hosts.
Upgrade the physical CPUs of the host.
Upgrade ESXi to the latest version.
Enable CPU-saving features such as TCP segmentation offload, large memory pages, and jumbo frames.
Increase the amount of memory allocated to the virtual machines, which may improve cached I/O and reduce CPU utilization.
Reduce the number of virtual CPUs assigned to virtual machines.
Ensure that VMware Tools is installed.
Compare the CPU usage of troubled virtual machines with that of other virtual machines on the host or in the resource pool. (Hint: Use a stacked graph.)
Increase the CPU limit, shares, or reservation on the troubled virtual machine.
Host: Memory usage is consistently 94% or higher. Free memory is 6% or less.
Virtual machine: Swapping is occurring. (Memory usage may be high or low.)
Likely Causes?
The host has insufficient memory resources to meet the demand.
Host: Memory usage is consistently 94% or higher. Free memory is 6% or less.
Virtual machine: Swapping is occurring. (Memory usage may be high or low.)
Potential Solutions?
Ensure that VMware Tools is installed and that the balloon driver is enabled for all virtual machines.
Reduce the memory size on oversized virtual machines.
Reduce the memory reservation of virtual machines where it is set higher than needed.
Add the host to a DRS cluster.
Increase the number of hosts in the DRS cluster.
Migrate one or more virtual machines to other hosts.
Add physical memory to the host.
Virtual machine: Memory usage is high.
Guest OS: Memory usage is high. Paging is occurring.
Likely Causes?
The guest OS is not provided sufficient memory by the virtual machine.
Virtual machine: Memory usage is high.
Guest OS: Memory usage is high. Paging is occurring.
Potential Solutions?
Increase the memory size of the virtual machine.
Virtual machine: CPU ready is low.
Guest OS: CPU utilization is high.
Likely Causes?
The guest OS is not provided sufficient CPU resources by the virtual machine.
Virtual machine: CPU ready is low.
Guest OS: CPU utilization is high.
Potential Solutions?
Increase the number of CPUs for the virtual machine.
Migrate the virtual machine to a host with faster CPUs.
Datastore: Space utilization is high.
Likely Causes?
Snapshot files are consuming a lot of datastore space.
Some virtual machines are provisioned with more storage space than required.
The datastore has insufficient storage space to meet the demand.
Datastore: Space utilization is high.
Potential Solutions?
Delete or consolidate virtual machine snapshots.
Convert some virtual disks to thin provisioned.
Migrate one or more virtual machines (or virtual disks) to other datastores.
Add the datastore to a Storage DRS datastore cluster. Add datastores with available space to the datastore cluster.
Add more storage space to the datastore.
Disk: Device latency is greater than 15 ms.
Likely Causes?
Problems are occurring with the storage array.
Disk: Device latency is greater than 15 ms.
Potential Solutions?
Migrate the virtual machines to datastores backed by other storage arrays.
Disk: VMkernel latency is greater than 4 ms. Queue latency is greater than zero.
Likely Causes?
The maximum throughput of a storage device is not sufficient to meet the demand of the current workload.
Disk: VMkernel latency is greater than 4 ms. Queue latency is greater than zero.
Potential Solutions?
Migrate the virtual machines to datastores backed by storage devices (LUNs) with more spindles.
Balance virtual machines and their disk I/O across the available physical resources. Use Storage DRS I/O balancing.
Add more disks (spindles) to the storage device backing the datastore.
Configure the queue depth and cache settings on the RAID controllers. Adjust the Disk.SchedNumReqOutstanding parameter.
Configure multipathing.
Increase the memory size of the virtual machine to eliminate any guest OS paging. Increase the guest OS caching of disk I/O.
Ensure that no virtual machine swapping or ballooning is occurring.
Defragment guest file systems.
Use eager zeroed thick provisioned virtual disks.
Network: The number of packets dropped is greater than zero. Latency is high. The transfer rate is low.
Likely Causes?
The maximum throughput of a physical network adapter is not sufficient to meet the demand of the current workload.
Virtual machine network resource shares are too few.
Network packet size is too large, which results in high network latency. Use the VMware AppSpeed performance monitoring application or a third-party application to check network latency.
Network packet size is too small, which increases the demand for the CPU resources needed for processing each packet. Host CPU, or possibly virtual machine CPU, resources are not enough to handle the load.
