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).
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.
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 benchmark measured the bandwidth of pod-to-pod and pod-to-service connections between two different nodes using [`iperf`](https://iperf.fr/).
GKE and Constellation on GCP had a maximum network bandwidth of [10 Gbps](https://cloud.google.com/compute/docs/general-purpose-machines#n2d_machineshttps://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).
- [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/).
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.
