Write speeds of both Disks A and B show the same reduction when connected via a Thunderbolt hub as reported previously.

Measured speeds in the same units and format were: Only one write speed shows any significant change, a fall from 2.2 to 1.8 GB/s, with the encrypted volume being 82% of the speed of plain APFS. Measured speeds, given as GB/s for read / write, were: Speeds were measured using the standard options in my free app Stibium, in each case over 160 files ranging in size from 2 MB to 2 GB, in random order, giving a total of 53 GB of test files.

This article reports estimates of the effect of reading from and writing to APFS encrypted volumes on three different high-speed Thunderbolt 3 SSDs, when connected direct to a Mac Studio M1 Max, and via a Thunderbolt 4 hub. When Apple first introduced whole-volume encryption, some considered it incurred a significant performance penalty, but more recent reports suggest that may be almost unnoticeable, at around 3-5% or less. If you want to store your backups securely or keep sensitive data safe, that encryption won’t be performed by the T2 chip or the Secure Enclave built into M-series chips. On all Macs, regardless of processor, using APFS Encrypted volumes brings overhead.

Whether or not you turn FileVault on, the T2 chip and M-series chips always encrypt Data volumes on the internal SSD, so enabling FileVault there incurs no penalty on internal storage. Intel Macs with a T2 chip and all Apple silicon Macs offer two types of encryption for APFS volumes: FileVault on the internal SSD encrypts the Data (and, in Catalina, the System) volume using hardware and encryption keys in the Secure Enclave, while APFS Encrypted volumes on other storage use software and store their keys separately.

Apfs encrypted