VMware vSphere offers three different types of clones including
- Full clone: a child VM that shares nothing with the parent VM after creation.
- Linked clone: a child VM that shares virtual disks with the parent VM.
- Instant clone: a child VM that shares virtual disks and memory with the parent VM.
Each type of clone has its own performance advantages, which we describe in the technical paper, Understanding Clones in VMware vSphere 7: Performance Study.
We look at clone performance with several workloads from industry-standard benchmarks. We show how running the different workloads affects these clones. The workloads include a Java server workload (SPECjbb 2015); an OLTP database (HammerDB); an in-memory, key-value store workload (memtier_benchmark); and a virtual desktop workload (View Planner).
The figure below shows the aggregate performance of child VMs when running the SPECjbb 2105 workload. In our tests, we varied the number of child VMs from 4 to 8 (of a full clone – FC/blue, of a linked clone – LC/orange, and of an instant clone – IC/green). We observed that the performance (measured in aggregate transactions per second) of full clones and linked clones is nearly identical in both the 4-clone and 8-clone scenarios. This is not surprising since SPECjbb 2015 is very CPU- and memory-intensive, but it has no disk-I/O component. For other workloads with a minimal disk-I/O component, we expect the performance of linked and full clones to be nearly identical as well.
To learn more about vSphere 7 clone performance, read the full paper.
NOTE: Our results are not comparable to SPEC’s trademarked metrics for this benchmark. Learn more about SPECjbb 2015.