In previous posts, I talked about vSAN Encryption architecture, and how to enable such feature. However, there are a couple of considerations aside from the requirements that should be taken into account prior to enabling vSAN Encryption.
With most deployments, whether it is vSphere, or vSAN; I’ve noticed that BIOS settings are often overlook, even though they can help increase performance with a simple change. One of those settings is AES-NI. AES-NI was proposed by Intel some time back, and it is essentially a set of [new] instructions (NI), for the Advanced Encryption Standard (AES); hence the acronym AES-NI. What AES-NI does, is provide hardware acceleration to applications using AES for encryption, and decryption.
Most modern CPUs (Intel & AMD), support AES-NI, and some BIOS configurations from certain hardware vendors already have AES-NI enabled by default. When considering vSAN Encryption, it is imperative to make sure that AES-NI has been enabled in the BIOS, in order to take advantage of such offloading of instructions to the CPU as well as strengthening, and accelerating the execution of AES applications.
Failure to enable AES-NI while Encryption is enabled, may result in a dramatic cpu utilization increase. In recent versions of vSAN, the Health Check UI detects, and alerts when AES-NI has not been enabled. If the BIOS does not have the option to enable AES-NI, it is most likely that the feature is always enabled.
Note: This also applies to VM encryption.
The other consideration is available space. My previous posts talk about data migration occurring if vSAN Encryption was enabled after data has been moved into the vSAN Datastore, due to the disk format task necessary. Although vSAN Encryption does not incur a space overhead for its operation, it is important to keep in mind that there needs to be enough available space to be able to evacuate an entire disk group during the configuration process.