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Does the BitLocker Encryption Impact Your Disk Performance?

People tend to security their disk partition by using BitLocker: it is also useless even if others create a boot disk to enter the Windows PE environment to offline get into your computer. However, someone doubts whether the BitLocker impact computer disk performance. So, I'm going to test the write and read speed in different encryption methods.

Different from the past, Microsoft uses XTS-AES encrypt algorithm after launching Windows 10 TH2. There are four encryption methods in total:

  1. 1. XTS-AES 128-bit (Default);
  2. 2. XTS-AES 256-bit;
  3. 3. AES-CBC 128-bit;
  4. 4. AES-CBC 256-bit.

The longer secret key is, the more security it is, the more difficult to be attacked. However, you would take more time to encrypt or decrypt the data if the secret key is longer. By default, you can change the method of BitLocker encryption via expanding Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption. In the right panel, double-click on "Choose drive encryption method and cipher strength" and find correct one via bracket explanation behind. So, you can refer to explain information for specific usage and directions.

choose drive encryption method and cipher strength

Test 1

Testing Environment

You can use a password or smartcard to unlock BitLocker in Windows 10. I decide to use a password to encrypt Disk D. Testing tool: I use ATTO Disk Benchmark to test my Disk D, for it is no applications installed on this disk and there won't have any read or write operation while testing.

HDD: SEAGATE Barracuda with 1TB capacity and 7200rpm, the specific type is ST1000DM010, 64MB cache.

Processor: Intel Pentium CPU G4400, dual-core dual-threaded, 3MB cache, clocked at 3.3GHz. The specification of CPU lists the technology that supports the AES New Instructions.

Windows system: Windows 10 Enterprise, 64-bit, 1709 version.

Testing result

I respectively use the transfer rate in different encrypt method and cipher strength to compare with the transfer rate of no encryption.

result of unencrypted encrypt with xts aes 128 bit

encrypt with xts aes 256 bit encrypt with aes cbc 128 bit

encrypt with aes cbc 256 bit

So, according to the comparison above, we can find that using BitLocker encryption has little influence on the reading rate while the writing rate has an obvious difference. Base on my usage habit, I use the read and write rate data of 8MB, 16MB, and 64 MB to make a simple compare.

1. Read/write Performance

read rate in test 1

write rate in text 1

2. Read/write performance loss

read rate loss in test 1

write rate loss in test 1

Test 2

Test environment

Testing tool: I use ATTO Disk Benchmark to test my Disk E this time.

SSD: TOSHIBA Q200EX, with 240G storage capacity, SATA3 port.

Processor: Intel Core i5-2430M CPU frequency 2.40GHz, the biggest Turbo frequency is 3.0G, dual-core four-threaded, 3MB cache.

Windows system: Windows 10 Enterprise 64-bit operating system, 1703 version.

Testing result

We have to compare the performance with different encryption methods and cipher strengths.

no encryption xts aes 128

xts aes 256aes cbc 128 bit

aes cbc 256 bit

Now use the read and write rate data of 8MB, 16MB, and 64 MB to make a simple compare.

1. Read/write performance

read performance in test 2

write performance in test 2

2. Read/write performance loss

read performance loss in test 2

write performance loss in test 2


From the data in Test 1, we can see that BitLocker encryption has 50% - 62% loss impact on writing performance in desktop computer. However, as to read performance, the BitLocker encryption impact can be ignored.

In Test 2, the read performance losses within 1% while the write performance losses about 5% (Except 64MB block in AES-CBC 128-bit encryption is abnormal, maybe due to another environment factor impacts it). In general application, they have more reading operation and less writing operation. As a whole, considering the practicality of BitLocker encryption, its overall impact on performance is negligible.

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