I've put a brand new SSD into my work computer and my IT department wants me to use BitLocker. I read one of the other threads on BitLocker performance on standard harddrives, but I was wondering - what's the performance impact of BitLocker like on a Solid State Drive?

Will it noticeably impact the speed with which I open my archive files in Outlook or open projects in Visual Studio?


11 Answers 11


You should have a negligible performance impact with most SSDs. Especially with the latest Intel CPUs that can do hardware AES way faster than a drive (any drive) can read or write. My MacBook Pro pushes over 900 megabytes per second with AES according to the TrueCrypt benchmark, and that's a laptop.

On my desktop I use 4 Samsung SSDs in RAID0 and I have BitLocker turned on. TrueCrypt on this same machine reports over 5GB/sec for AES. (Two 6-core Xeons...)

That said, the SandForce SSD controller is said to do some internal compression/dedupe (which was proven via benchmarks that used large compressed files that it could not "optimize"). Obviously this is not going to work at all with BitLocker where every encrypted sector will be completely unique and uncompressible. So if you're planning on using an SSD, don't get a SandForce one - or if you do, make sure you can return it if you find that performance really degrades after you turn BitLocker on.

  • 5
    +1 for mentioning SandForce. Data with very high entropy, like encrypted data, breaks one if the fundamental assumptions that their controllers are built on. BitLocker will be bad for those drives compared to, say, an Intel drive.
    – afrazier
    Jan 20, 2011 at 0:27
  • 2
    Thx... I would love to see a benchmark that compares BitLocker/TrueCrypt vs. "naked" performance on these much-hyped drives. I suggested it to Anand and he brushed it aside. Anyone with a link to a good one gets a +1 on their comment. :)
    – martona
    Jan 20, 2011 at 1:04
  • @afrazier @martona Some SandForce drives, such as the Vertex 2, already do "self-encryption" in hardware on all data using AES 128-bit. This involves an ATA password at startup (see comments here), rather than an OS-level password.
    – sblair
    Jan 26, 2011 at 18:50
  • @sblair: That's interesting to know, though ATA passwords can be pain to deal with compared to things like enterprise deployment of BitLocker w/ TPM integration. It just depends on the environment and the users. Thank you for the link!
    – afrazier
    Jan 26, 2011 at 20:23
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    There will be some noticeable degradation of performance. Even if your CPU can encrypt gigabytes of data per second, there is still a time penalty for doing so on every read or write, and a CPU load penalty. How bad this is depends entirely on the application, but it is easily measurable in benchmarks and noticeable in real world applications.
    – user237698
    Oct 14, 2014 at 9:10

Because BitLocker does not really change the usage characteristics of the drive other than changing the data itself (e.g. it does not cause the OS to write randomly instead of linearly), it should have the same impact on an SSD that it would have on platters. That is, I would still expect the 20%-10% decrease in performance that MaximumPC found, as mentioned in the thread you link to. Note that the speed of BitLocker may be bottlenecked by either the processor or the drive. That is, if the processor can encrypt/decrypt faster than the drive can read/write data, then file I/O will occur at near the speed of the drive. If your processor is overtaxed, the processor may limit file I/O speed (although I believe hardware-accelerated cryptography should minimize the likelyhood of this happening).

  • 7
    This answer appears now to be rather out of date. The performance and wear-levelling implications of incompressible data are very different with the current generation of SSD's compared to the last generation of SSD's. See more recent answers, which haven't had as much chance to get voted up.
    – Mark Booth
    Nov 22, 2011 at 14:26
  • 1
    I wonder what's the current status then
    – matanox
    Dec 20, 2017 at 18:06
  • There's another reason this answer is no longer valid (or never was valid) -- TRIM. Unencrypted SSDs can use TRIM data to erase blocks belonging to erased data; write performance improves as the block is now immediately writeable when needed. Free space with Bitlocker isn't the same as empty space.
    – apraetor
    Feb 9 at 17:11

UPDATE: Some tests claim lower impact on modern hardware https://superuser.com/a/1637950/89990

On Dell Inspiron 15 7577 Intel i7-7700HQ Samsung 950 PRO 256GB NVMe Windows 10 64 bit NTFS I see indication of performance penalty by Bitlocker on small random files(e.g. compilation process), VeraCrypt is bad, transient(no need to encrypt) in memory is fast (e.g. get more memory, script mount of in memory disk and copy of files for compilation).

Not encrypted:

Not encrypted

Encrypted by BitLocker:

Encrypted by BitLocker

Encrypted by VeraCrypt 1.21:

Encrypted by VeraCrypt

ImDisk 2.0.9 in memory:

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  • 1
    👏 excellent detailed info, thanks for sharing this! Have any updates for newer hardware? Mar 27, 2021 at 21:03
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    I have the latest hardware as of 2020 with 2X faster NVMes and all Windows updates. I do use Bitlocker(OS) and Veracrypt(keys) for different datas. What I do not do - I do not encrypt any source codes for compilation. Even if encryption improved, I still do not want to pay anything for it during compilation. Also, I believe Windows-Hardware updates could improve situation indeed, but I do not care. And that report was done, partially, to fact against lie of big company IT dep about encryption does not hurts perf at all (of course I do not work tere now:) . Mar 28, 2021 at 6:53
  • 1
    I did find more updated info, adding an answer! Mar 29, 2021 at 16:30

I do not know if what applies to Truecrypt applies to bitlocker, but on SSDs, Truecrypt has a hugely negative impact on performance if you encrypt the entire disc.

The root cause of the problem is that you can no longer tell the difference between free space and usable space because encrypted data and encrypted free space are both treated as data. This defeats both TRIM and any wear-leveling optimizations.

The performance on reads is negligible, but on average you are cutting your write performance by half or more. There is some evidence that leaving a free empty partition (i.e. giving the wear leveling algorithms, which factor into performance, room to work with) has a huge positive benefit, but TRIM does leak data and can theoretically be used to compromise an encrypted partition by someone with enough resources.

EDIT: This might no longer be true because of "TRIM Passthrough" features that now exist, but there is a lot of very tangled information out there when googling exactly how this behaves. I would love to see some actual benchmarks with TrueCrypt 7.0 and FDE (older versions of TC will display the problems I talked about above), but I cannot find any!

EDIT2: Some years later the situation is now different yet again. Almost all SSDs encrypt the data before writing it because you want your data at the physical level to have high entropy. In most drives the keys to do this were not user accessible, now with OPAL they can be set by the OS to give you AES encryption for no performance penalty! You need both OS and Hardware support for this to work.


On modern hardware, the perf impact is very low! This is on AMD R7 4800HS CPU, and Intel 665p NVMe SSD:

bitlocker perf impact

  • Comparing disk performance is one thing… with a fast-enough CPU / memory combo, that delta should approach zero. What about CPU / power impact, though? Aug 8, 2022 at 15:56

I've been running Windows 7 Ultimate 64 Bit, using a SSD (120 GB) for about 5 months. I'm using a 1TB HDD (middle to high end) at 7200RPM as my comparison. First the test involved simply clocking the OS start up time. Although it was not lightning fast it was apprx. 2 times faster than the HDD. Only testing larger files (at least 1 GB) there was also a significant increase in speed. Relatively, across the board, the SSD is faster than the HDD!

Bitlocker; however, has had serious conflicts with the SSD. My experience has shown that there's a strong likely hood they're not made for each other. The main problem is that the volatile nature of SSD causes Bitlocker to believe that there has been a change in the hardware configuration even when no such change has taken place. The end result is an ongoing request for passwords and/or Bitlocker recovery keys.

Whether it be a fault in the SSD, Bitlocker, or both, the machine stopped accepting passwords and recovery keys all together. After receiving my RMA, encrypting the drive and using as usual, the exact (change of Hardware Config.) problem reoccurred. After decryption of the drive I've had no problems and performance has been very good! Needless to say sacrificing a large amount of security.

SSD does offer a big increase in performance. Windows Experience before: 5.9 Windows Experience After: 6.9

  • 1
    I (and thousands of others) use BitLocker on SSD without the problems you mention. I would guess your problem stems from an incompatibility between components of the PC or maybe firmware bugs, that have been long solved by now (2016). Dec 27, 2016 at 13:14

My companies testing of Bitlocker on windows 7 showed that with a laptop with a 7200RPM drive as well as an Intel SSD, they both had about 5% reduction in speed. However, for the very first task of initializing bitlocker, the HDD took about 4 hours, and the SSD was dramatically faster (both drives were 160GB drives)

However, the laptops had some new fancy Core i5 processors, and chip sets, and could offload the encryption off of the main CPU.


Are you open to running Windows 8? Do you have a TPM chip in your laptop, and is your laptop UEFI capable?

There are TCG OPAL SSD drives out there. I have not found a Sandforce based drive that supports this, but Micron has one: Micron C400 SED. You have to make sure you buy the SED version, not the plain version. Using an OPAL compliant drive will allow you to use Bitlocker in Windows 8 in conjunction with the drive's encryption (which it's already doing).

Bitlocker in this scheme does not actually do any encryption from the system side (at least for data read/written). The bulk of Bitlocker in this mode is acting as a "Gatekeeper" since SED drives still need a means of access control to unlock the drive. When those are activated in this mode (with W8 and Bitlocker), the drive is initially locked and the system will only show a very small "shadow partition" under 200MB. This is where the W8 boot files are stored and the unlocking in Bitlocker happens with it interacting with TPM to pass a key to unlock the drive.

If you don't want to go Windows 8, you lack TPM (though I assume you have it since they asked you to enable bitlocker), or BIOS instead of UEFI there are a number of software products that can manage SED drives in place of Bitlocker.

In my experience, Bitlocker does in fact have a noticeable degradation in performance even with HDDs. With SSDs, the comparisons I've seen seem to indicate the degradation is worse, perhaps enough that a lot of the benefits to SSD is reduced. In my view, a SED based SSD with Bitlocker management (or another software piece) is the best way to go.

  • Anyone know if recent versions of Bitlocker still use OPAL as of 2022?
    – Simon E.
    Jun 7, 2022 at 7:37
  • It would also be interesting to know how the power usage of a SED compares to an identical non-SED drive (or SED with encryption disabled, if that is possible). The built-in encryption processor ~must~ require some power, right? Aug 8, 2022 at 16:01

There are 2 important aspects here:

TRIM and SandForce.

Bitlocker, unlike TrueCrypt, supports TRIM (leaves empty parts empty and unencrypted). This has security implications but performance wise this allows the drive to do more garbage collecting and avoids performance degradation over time.

SandForce controller is a popular SSD controller, which gains significant performance boosts though data compression. Encrypted data does not compresses (it looks random and unpredictable by design). If you need full disk encryption you should prefer a different controller (try Samsung).

  • 1
    Part of this information is not correct. Truecrypt does support TRIM. See here, for instance. Aug 24, 2015 at 11:29

Thanks for asking that question.

I've been running the most current version of AS SSD on the various SSDs I have around. (Intel, Kingston, OCZ RevoDrive, Corsair, Samsung, Crucial). I run an AS SSD session monthly. Interestingly the Intel is the only one that stayed on a stable 690-720 Score. Probably due to the SSD Toolkit that runs weekly. The others deteriorated a couple of numbers every month.

That is until I activated BitLocker on my Lenovo T430S. Now the score of the Intel is down to 580 consistently.


I turn on BitLocker in a tablet and laptop with Windows 10.

In tablet:

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

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

In laptop:

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. BitLocker causes 50% - 60% performance loss in tablet while no influence on the laptop.

To find out whether processor effects or not, turn on BitLocker on a tablet with Windows 7.

Here are details:

HDD: SEAGATE Barracuda ST1000DM003, 1TB capacity, and 7200rpm, 64Mb cache.

Processor: Intel Xeon E3-1203 v3, quad-core eight threads, 8MB cache, 3.3GHz clock speed and Intel Turbo Boost allows users to increase the clock rate to 3.70 GHz. The specification of CPU lists the technology that supports the AES New Instructions.

From the result, this still has 50% write rate decreases. Therefore, the Processor doesn't impact performance at all. Then I do an in-depth study of how BitLocker effect on read-write performance. SSD with AES chip inside would be affected less by turning on BitLocker.

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