My company mandates Software Encryption for all laptops.

I dragged my feet because I did not want to have anything between me and my data. But I was finally pushed into it.

I installed it and I am not noticing much of a difference yet (yay!). I wanted to measure what actual difference (if any) there was.

So I took note of my Primary hard disk "Disk data transfer rate" index from Windows Experience before and after I had the encryption installed.

To my surprise the number is the same (5.9).

So I am left wondering if there really is not difference, or if the "Rate of data" is the same because it is measuring after the encryption is done.

Does anyone know why the value would be the same?

2 Answers 2


If you have recent CPU (and the encryption software is written intelligently (as it should)) it should use your cpu extensions (don't know which ones, but I know Intel Core i3, i5, i7 has it) to ease the encryption process. (Without those extensions it works the same too, but the performance is dropped down as CPU has more work to do, but it isn't too much). But... classic HDDs are slow, CPU is fast, that means the highest performance hit is in the disk, not in the CPU, even when you copy X GB file and encrypting it at once.

When you have SSD disk, the case is whole different. The performance drop is higher compared to raw SSD read/write throughput.

[I've read this when I studied how FileVault 2 on my Mac works and, like you, I was concerned about performance.]

Also, it should do the encryption when the CPU is in it's idle state. So when you are doing normal work (and not copying X GB file for example) you shouldn't notice the performance drop (even if you don't have those supporting extensions) at all.


Please note that 5.9 is currently the maximum possible value for Windows Experience Index. E.g. 5.9 only means "faster than XXX" for some value of XXX. You could have a real performance drop, and still have a 5.9 disk index if your performance is still above XXX.

Moreover, software encryption means higher CPU utilization during disk writes and reads (naturally data needs to be encrypted/decrypted). So if your CPU(s) is/are idle, there might be a very little encryption overhead, but if your processor is fully loaded, disk performance might drop significantly.

In my experience, full-disk encryption done right does not affect a modern laptop system significantly, when the load is regular office programs.

But if you're building a large software project, several compilations in parallel, large output files, etc., build times are significantly longer.

  • 5.9 is currently the maximum possible value - Don't confuse max base score with the individual subsystem subscores, which can be more than 5.9. E.G. a solid-state drive will score better than 5.9.
    – sawdust
    Dec 9, 2011 at 7:54

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