Bitlocker can cut SSD performance in half

One of the main differences between the Home and Pro versions of Windows 11 is that Windows 11 Pro includes disk encryption using Bitlocker. It protects all data on C: from access if someone steals your computer, and is typically enabled on business computers – especially laptops that are more vulnerable to theft.

Bitlocker is automatically enabled on most Windows 11 computers, as these devices already have everything required for it: a TPM, Secure Boot, and HSTI. In the past, only a few people had these features enabled because Windows 10 and earlier didn’t require it, and only casual users and more security-conscious businesses cared.

Those with Windows 11 Pro may miss out on a lot of disk performance because of this. Tom’s devices We tested the performance impact of activating Bitlocker and with a fast SSD on a powerful desktop, the difference was significant, especially for random writes. On PC Mark 10, the site’s test disk, a 4TB Samsung 990 Pro, gets roughly 600MB/s without encryption and 490MB/s without encryption. This applies to Bitlocker which is controlled by software. Many modern SSDs have built-in support for disk encryption and with this feature enabled in the Samsung disk, it shows a slightly higher speed without any encryption.

Crystaldiskmark shows that the difference increases for random reads and writes of small files. The biggest difference is when writing, where Bitlocker reduces performance by up to 45 percent, but even random reads without a queue (the “4K QD1” test) show a 20 percent drop when Bitlocker is enabled.

However, for sequential reads and writes, the difference is minimal, and in some tests, the Bitlocker version produced the fastest results. But small, random files make up the majority of disk activity for most people, with the exception of video editing, for example.

Testing shows that Bitlocker has a clear negative impact on SSD performance, but whether this measurable performance loss is noticeable to the user in everyday computer use is another question.