vSAN Encryption at Rest & In Transit: What is the difference?

In the past, I’ve written a few posts about vSAN Data-at-Rest Encryption, which became available with vSAN 6.6. You can find those posts here. In vSAN version 7.0U1 there is a new option for encryption, Data-In- Transit Encryption. So what is the difference? Can I only choose one or both? Let’s find out.

vSAN Data at Rest Encryption

Data-at-rest (D@RE) was designed to do just that. Encrypt all your data once it lands on the disks being used by vSAN. This will work regardless the Storage Policy you choose, and all the data replicas will be encrypted at both the cache layer and the capacity layer. One major advantage of Data-at-Rest Encryption over the vSphere VM encryption is that vSAN will still allow you to encrypt your data and take advantage of space saving features such as deduplication and compression. When the data lands in cache it will be encrypted using the Data Encryption Key (DEK), then while the data is being destaged to the capacity layer it will be decrypted, and it is here where the deduplication and compression takes place. Finally when the data lands in the capacity devices, the data gets encrypted once again. It is also important to highlight that the DEK is protected by the Key Encryption Key (KEK) which is coming from the Key Management Server (KMS)… and this is one of the differences between the two options.

vSAN Data in Transit Encryption

Data-In-Transit Encryption (DIT) comes in to complete the end-to-end encryption of the data while in transit between hosts. Data-at-Rest encryption only encrypts the data when it lands on disk, so if someone takes a disk out of a server, all data is encrypted. But what about other attacks such as Man-in-the-middle attacks? Well, this is where Data-In-Transit encryption can protect the data. The keys used for DIT encryption are managed internally and there is no need for a KMS. Such keys are also rotated much, much faster when compared with D@RE. DIT encryption keys are rotated weekly by default, but you can change this option and rotate keys either every 7 days or every 6 hours or something in between. Just like D@RE encryption, DIT encryption works at a vSAN cluster level; so either all the hosts are protected or none.

Here is a quick comparison between the two options


Can I enable both at the same time?

Yes. You can enable Data at rest and Data in Transit encryption in order to get full protection in your vSAN environment. It is recommended to enable vSAN Data at Rest encryption in the early stages of the cluster to minimize the time for on-disk formatting as there is less data to move around.

What is the performance impact of turning encryption on?

There are a lot of variables that come in to play when we talk about performance. However; vSAN encryption (both) will take advantage of AES-NI and offload operations in order to reduce any performance hit. Most modern CPU have AES-NI, but sometimes this feature is not enabled, so make sure to check this at deployment. Please also be mindful that enabled D@RE when the cluster has a lot data in it will result in large amounts of data being moved, so plan this to be done during off hours if possible.

What vSAN License do I need to enable vSAN Encryption?

In order to enable Data-at-Rest and/or Data-In-Transit Encryption you will need vSAN Enterprise or vSAN Enterprise Plus licenses. Refer to licensing guide here.

How do I enable Data-In-Transit Encryption?

Enabling DIT encryption is easy. Within the vCenter UI, select the vSAN cluster > Configure > Services > Data-In-Transit can be enable with or without Data-at-Rest encryption. Here is where you can also change the key rotation schedule for the DIT encryption keys.


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