This section analyzes the performance of Constellation.
## Performance impact from runtime encryption
All nodes in a Constellation cluster run inside Confidential VMs (CVMs). Thus, Constellation's performance is directly affected by the performance of CVMs.
AMD and Azure jointly released a [performance benchmark](https://community.amd.com/t5/business/microsoft-azure-confidential-computing-powered-by-3rd-gen-epyc/ba-p/497796) for CVMs based on 3rd Gen AMD EPYC processors (Milan) with SEV-SNP. With a range of mostly compute-intensive benchmarks like SPEC CPU 2017 and CoreMark, they found that CVMs only have a small (2%--8%) performance degradation compared to standard VMs. You can expect to see similar performance for compute-intensive workloads running with Constellation on Azure.
Similarly, AMD and Google jointly released a [performance benchmark](https://www.amd.com/system/files/documents/3rd-gen-epyc-gcp-c2d-conf-compute-perf-brief.pdf) for CVMs based on 3rd Gen AMD EPYC processors (Milan) with SEV-SNP. With high-performance computing workloads like WRF, NAMD, Ansys CFS, and Ansys LS_DYNA, they found similar results with only small (2%--4%) performance degradation compared to standard VMs. You can expect to see similar performance for compute-intensive workloads running with Constellation on GCP.
To assess the overall performance of Constellation, this benchmark evaluates Constellation v2.6.0 in terms of storage I/O using [`fio`](https://fio.readthedocs.io/en/latest/fio_doc.html) and network performance using the [Kubernetes Network Benchmark](https://github.com/InfraBuilder/k8s-bench-suite#knb--kubernetes-network-be).
This benchmark tested Constellation on Azure and GCP and compared the results against the managed Kubernetes offerings AKS and GKE.
On AKS, the benchmark used Kubernetes `v1.24.9` and nodes with version `AKSUbuntu-1804gen2containerd-2023.02.15`.
AKS ran with the [`kubenet`](https://learn.microsoft.com/en-us/azure/aks/concepts-network#kubenet-basic-networking) CNI and the [default CSI driver](https://learn.microsoft.com/en-us/azure/aks/azure-disk-csi) for Azure Disk.
The following infrastructure configurations was used:
On GKE, the benchmark used Kubernetes `v1.24.9` and nodes with version `1.24.9-gke.3200`.
GKE ran with the [`kubenet`](https://cloud.google.com/kubernetes-engine/docs/concepts/network-overview) CNI and the [default CSI driver](https://cloud.google.com/kubernetes-engine/docs/how-to/persistent-volumes/gce-pd-csi-driver) for Compute Engine persistent disk.
The following infrastructure configurations was used:
- Nodes: 2 (2 Worker)
- Machines: `n2d-standard-4` 2nd Generation AMD EPYC (Rome) processor with 4 Cores, 16 GiB of memory
GKE and Constellation on GCP had a maximum network bandwidth of [10 Gbps](https://cloud.google.com/compute/docs/general-purpose-machines#n2d_machines).
AKS with `Standard_D4as_v5` machines a maximum network bandwidth of [12.5 Gbps](https://learn.microsoft.com/en-us/azure/virtual-machines/dasv5-dadsv5-series#dasv5-series).
The Confidential VM equivalent `Standard_DC4as_v5` currently has a network bandwidth of [1.25 Gbps](https://learn.microsoft.com/en-us/azure/virtual-machines/dcasv5-dcadsv5-series#dcasv5-series-products).
Therefore, to make the test comparable, both AKS and Constellation on Azure were running with `Standard_DC4as_v5` machines and 1.25 Gbps bandwidth.
- Constellation's [network encryption](../architecture/networking.md) via Cilium and WireGuard, which protects data in-transit.
- [AMD SEV using SWIOTLB bounce buffers](https://lore.kernel.org/all/20200204193500.GA15564@ashkalra_ubuntu_server/T/) for all DMA including network I/O.
In our recent comparison of Constellation on GCP with GKE, Constellation has 58% less TCP bandwidth. However, UDP bandwidth was slightly better with Constellation, thanks to its higher MTU.
Similarly, when comparing Constellation on Azure with AKS using CVMs, Constellation achieved approximately 10% less TCP and 40% less UDP bandwidth.
Azure and GCP offer persistent storage for their Kubernetes services AKS and GKE via the Container Storage Interface (CSI). CSI storage in Kubernetes is available via `PersistentVolumes` (PV) and consumed via `PersistentVolumeClaims` (PVC).
Upon requesting persistent storage through a PVC, GKE and AKS will provision a PV as defined by a default [storage class](https://kubernetes.io/docs/concepts/storage/storage-classes/).
Constellation provides persistent storage on Azure and GCP [that's encrypted on the CSI layer](../architecture/encrypted-storage.md).
Similarly, upon a PVC request, Constellation will provision a PV via a default storage class.
For Constellation on Azure and AKS, the benchmark ran with Azure Disk storage [Standard SSD](https://learn.microsoft.com/en-us/azure/virtual-machines/disks-types#standard-ssds) of 400 GiB size.
The [DC4as machine type](https://learn.microsoft.com/en-us/azure/virtual-machines/dasv5-dadsv5-series#dasv5-series) with four cores provides the following maximum performance:
However, the performance is bound by the capabilities of the [512 GiB Standard SSD size](https://learn.microsoft.com/en-us/azure/virtual-machines/disks-types#standard-ssds) (the size class of 400 GiB volumes):
For Constellation on GCP and GKE, the benchmark ran with Compute Engine Persistent Disk Storage [pd-balanced](https://cloud.google.com/compute/docs/disks) of 400 GiB size.
The N2D machine type with four cores and pd-balanced provides the following [maximum performance](https://cloud.google.com/compute/docs/disks/performance#n2d_vms):
However, the performance is bound by the capabilities of a [`Zonal balanced PD`](https://cloud.google.com/compute/docs/disks/performance#zonal-persistent-disks) with 400 GiB size:
On GCP, the results exceed the maximum performance guarantees of the chosen disk type. There are two possible explanations for this. The first is that there may be cloud caching in place that isn't configurable. Alternatively, the underlying provisioned disk size may be larger than what was requested, resulting in higher performance boundaries.
When comparing Constellation on GCP with GKE, Constellation has similar bandwidth but about 10% less IOPS performance. On Azure, Constellation has similar IOPS performance compared to AKS, where both likely hit the maximum storage performance. However, Constellation has approximately 15% less read and write bandwidth.
Despite the added [security benefits](./security-benefits.md) that Constellation provides, it only incurs a slight performance overhead when compared to managed Kubernetes offerings such as AKS and GKE. In most compute benchmarks, Constellation is on par, and while it may be slightly slower in certain I/O scenarios due to network and storage encryption, we're confident that we can reduce this overhead to single digits.
For instance, storage encryption only adds between 10% to 15% overhead in terms of bandwidth and IOPS. Meanwhile, the biggest performance impact that Constellation currently faces is network encryption, which can incur up to 58% overhead on a 10 Gbps network. However, the Cilium team has conducted [benchmarks with Cilium using WireGuard encryption](https://docs.cilium.io/en/latest/operations/performance/benchmark/#encryption-wireguard-ipsec) on a 100 Gbps network that yielded over 15 Gbps, and we're confident that we can provide a similar level of performance with Constellation in our upcoming releases.
Overall, Constellation strikes a great balance between security and performance, and we're continuously working to improve its performance capabilities while maintaining its high level of security.
