Test metrics
The performance of live guest relocations was evaluated using the metrics outlined in this section.
- Relocation time
- The elapsed time of the complete relocation process.
- Quiesce time
- The elapsed time while the relocated system is quiesced; during this time, the guest virtual system is prevented from performing any work. The quiesce time is the most prominent metric when evaluating the impact of the guest relocation process, because the virtual system is stopped for that period.
- Number of memory passes
- The number of passes that z/VM® performs when transferring the virtual memory of a guest virtual machine during a live guest relocation. Because the guest virtual machine continues its work while the live guest relocation is performed, that work may cause changes of memory content that was already transferred in a previous pass. Consequently, the modified memory content must be transferred in a subsequent memory pass.
- Amount of memory transferred
- During the relocation process overall, during various passes of the relocation process, and during the quiesce time. Depending on the update rates, this can be a multiple of the used resident memory.
- Linux™ steal time
- The percentage of time a virtual CPU waits for a real CPU while the hypervisor is doing other activities such as servicing another virtual processor
- fio throughput
- The average throughput (in MiB/s) achieved by all fio jobs together, averaged over the complete test duration, including the time needed for the relocation process.