Kernel Confusion

Bitlocker is a nice piece of security technology. My company, working mainly in IT consulting, uses only notebooks and of course needs to transport sensitive data from time to time. So, since Vista we use BitLocker to protect our valuable information from theft, e. g. in case of a stolen notebook. We also deployed it for some customers.

One question is always asked: what about the performance loss?  I don’t have much knowledge about how exactly BitLocker works under the hood, but I of course had the general experience that BitLocker secured systems are not slow at all. So I got myself a second hard drive for my notebook and ran a small test to clarify this question based on my hardware. This benchmark was mainly intended for me, but I decided to share the data anyway.

The test machine:
Lenovo ThinkPad T61, Intel Core2Duo T7500 2.2 GHz, 4 GB RAM
Hitachi HDD, SATA, 2.5″, 100 GB, 7200 RPM
Windows 7 Enterprise x64

I used ATTO as the benchmarking tool. The test process was simple: two runs without BitLocker, two runs with it.

The Result

For the read-performance there wasn’t a real performance drop, as you can see in the screenshots.
The write-performance dropped by about 4.5%. In my opinion, that isn’t bad at all. I’ve seen worse results for TrueCrypt and others, but I don’t want to compare software here.

Now of course, one has to decide how to interpret the result. Obviously it is limited to the used hardware, but I would say it won’t be any worse on a ThinkPad T500. Then again, this was a synthetic benchmark which does not reflect the normal workload or work-pattern. Anyway, my “feeling”, the performance-loss cannot be high, is backed up.