Solved HDD and SSD performance vs flash drives when BitLocker is used

I use BitLocker. A lot. One of the things I use it for is to secure personal data that I save on flash drives. But there are also partitions on HDDs and SSDs that I secure with BitLocker.

On either an SSD or a HDD, BitLocker doesn't slow me down in any noticeable way at all. I've specifically tested this and found that I can blast data to a disk very rapidly (several GB per second on a good NVMe drive). Remove BitLocker and I see no performance increase. So this indicates that BitLocker isn't slowing me down.

However, flash drives behave differently for some strange reason. I have a few good flash drives to which I can easily write in excess of 200MB per second if the drive is not BitLocker protected. However, enable BitLocker and I may only get something like 20MB per second (if I'm lucky).

I'm having a tough time wrapping my head around what the difference is. If I can maintain several GB per second to an NVMe drive, then clearly the system can encrypt the data at a very rapid rate so why the lousy performance to a flash drive?

If anyone has some thoughts or theories, I'd love to hear those.

Be aware the use of BitLocker will cause about a 1 percent performance hit (per Microsoft).

That said, I use BitLocker on my desktops (NVMe/SSD) and it hasn't caused any noticeable issues/performance drops where I needed to disable. Haven't tried it on flash drives

I use BitLocker on 2 of 3 laptops. It is used on both internal drives, 1 SSD and 1 HardDrive each. Also I use it on several flash drives and they work fine just as one would expect. I don't notice any performance issues or any thing else.

For me, I have no degradation of performance anywhere with BitLocker (at least, nothing noticabale) except on my flash drives. Yesterday I completely wiped a flash drive, then created two partitions - one with BitLocker, one without. The same data copies to the non-BitLocker partition almost ten times faster. No clue why.

In any case, I have well over 100 flash drives but I'm transitioning away from them to SSDs.

hsehestedt said:

For me, I have no degradation of performance anywhere with BitLocker (at least, nothing noticabale) except on my flash drives.

Click to expand...

Run a benchmark with and without as I did. Anyway, this is what Microsoft says...

Is there a noticeable performance impact when BitLocker is enabled on a computer?

Typically, there's a small performance overhead, often in single-digit percentages, which is relative to the throughput of the storage operations on which it needs to operate.

Click to expand...

Source: BitLocker deployment and administration FAQ (Windows 10) - Windows security

That said, it's not something you'll notice. The only way I found out (realized) was when I ran a speed test on my drives. Was wondering why I wasn't getting the numbers I expected and found it was BitLocker. Did it make me disable BitLocker... no. Is it impactful... no.

I've run benchmarks in the past. As I said, all is well except on flash drives for me. I go from 200+ MB/s down to under 20 MB/s.

Would have been nice to know why but I've put a new strategy into play, so it now no longer matters to me

Just FYI. Do with it what you will :)