Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?

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  1. Posts : 4
    Win 10 Pro 1909 (18363.1440) and 20H2 (19042.867).
       #1

    Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?


    More accurately:

    What would cause a considerable speed difference between Bitlocker enabled HDD's in Win 10 Pro 1909 (18363.1440) and Win 10 Pro 20H2 (19042.867).

    My Specs:

    i9 9900K
    Z390 Master mobo
    64GB DDR4 (3200 cl14)
    GTX 1080 GPU - 2 mons @ 2k
    GTX 1030 GPU - 2 mons @ 2k
    EVGA 750 W gold GPU
    Win 10 Pro on 500 GB 970 EVO NVMe
    (Windows 10 Pro versions and builds specific to issue below)
    2 TB 870 EVO SSD
    5 Hard Drives:
    6 TB Black HDD 7200
    5 TB Black HDD 7200
    3 TB Black HDD 7200
    3 TB Toshiba HDD 7200
    4 TB HGST HDD 7200

    Hi all,

    I build and maintain my own PC's. On my current main build I've encountered a problem where my Bitlocker encrypted mechanical hard drive speeds dropped very considerably after I did a fresh install this week of Win 10 Pro 20H2 (19042.867)

    Previously I was running Win 10 Pro 1909 (18363.1440) About a year ago I enabled Bitlocker's default XTS-AES 128 bit, on My OS C drive (500 GB 970 NVMe) and all HDD's. Afterward speeds were still fine (maybe ~ 5 % speed hit w Bitlocker enabled)

    Then this week I did a fresh install of Win 10 Pro 20H2 (19042.867). Before doing the install I disconnected all 5 of the other Bitlocker enabled hard drives in the PC, just leaving the NVMe OS drive. I secure erased the NVMe, then installed the OS from an MS sourced Win 10 Pro ISO. The install went fine, no probs.

    After install I enabled bitlocker (XTS-AES 128 bit) on the C drive. So this is now 20H2 (19042.867). When I benched the drive, the speeds compared to Win 10 Pro 1909 had dropped anywhere from 5 - 20%, depending on test parameter, test size, real world transfer tests. It's odd, but still not a super big deal as the NVMe is already fast and I was just going to live with the reduced speed differences I was encountering between the two OS installs, both with Bitlocker enabled.

    But the real problem was when I reconnected the HDD's. I used the same Bitlocker enabled HDD's that I was using on the previous Bitlocker enabled 1909 OS. I just shut down the PC, reconnected the HDD's, booted up, password unlocked them in Windows and turned on auto-unlock. When I went to test them, the write speeds had tanked.

    For Brevity I won't include all the screenshots of all tests ( that's probably 60 + tests including synthetic CrystalDiskMark, AS SSD & ATTO tests, and observing real world transfers in Win 10 Task manager and Win cut / copy / paste transfer window)

    But here is a couple examples:

    Comparison 1:

    5 TB WD Black HDD Win 10 Pro 1909 (18363.1440)
    CrystalDisk 1 GB Test (Bitlocker enabled)

    Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?-e-5-tb-wd-black-win-10-1909-diskmark-1-gb-test-encryption-2020-09-19.jpg

    5 TB WD Black HDD Win 10 Pro 20H2 (19042.867)
    CrystalDisk 1 GB Test (Bitlocker enabled)

    Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?-e-5-tb-black-win-10-20h2-diskmark-1-gb-test-encryption-2021-04-09.jpg

    That's roughly a 40 % drop.

    ---------------------------------------------------------------------------

    Comparison 2:

    6 TB WD Black Win 10 Pro 1909 (18363.1440)
    CrystalDisk 1 GB Test (Bitlocker enabled)


    Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?-g-6-tb-wd-black-win-10-1909-diskmark-1-gb-test-encryption-2020-09-19.jpg

    6 TB WD Black Win 10 Pro 20H2 (19042.867)
    CrystalDisk 1 GB Test (Bitlocker enabled)

    Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?-g-6-tb-black-win-10-20h2-diskmark-1-gb-test-encryption-2021-04-09.jpg


    That's roughly a 45 % drop

    ------------------------------------------------------------------------------


    I could post more similar screenshots if you want, but suffice to say all 5 of the Bitlocker enabled HDD's had these kinds of ~ 40 % speed drops between the Win 10 1909 and Win 10 20H2 install. Again for clarity, Bitlocker is enabled in both OS comparison cases, same Bitlocker XTS-AES 128 bit method, and it's the same PC components. So this is not something that I would necessarily attribute to enabling Bitlocker itself. Bitlocker On / Off comparisons in Win 10 1909 gave only ~ an avge 5 - 8 % speed hit.

    And real world transfer tests bear out even more dismal results in the 20H2 tests.

    Example:

    On the Bitlocker enabled HDD's in Win 10 1909, when I would do a large file transfer, the drive would start with it's burst speed, often as much as 2 GB/s, then drop to a steady 120 - 130 MB/s avge.
    On the Bitlocker enabled HDD's in Win 10 20H2, when I do a large file transfer, I still get decent burst speeds
    for a couple seconds, but then the transfer drops to between 20 - 40 MB/s for the duration of the transfer. Like USB 2.0 speeds, and sometimes even slower. That's about an 80 - 90 % slowdown on all the HDD's.

    I keep current Win 10 OS images of all installs. Thinking this was an anomaly I erased the 20H2 OS on the NVMe and restored the 1909 install from an image. Boom! Back to great HDD disk speeds as measured in synthetic benches and real world tests.

    In both installs (Win 10 1909 and 20H2) write caching is enabled for all drives via Device Mgr > Properties > Policies

    Bitlocker enabled HDD speed difference between Win 10 1909 and 20H2?-2021-04-12-write-caching-enabled-drive-properties.jpg

    In the Z390 Master F8 BIOS I have always set SATA to AHCI. In the 20H2 slow drive scenario I decided to just do a test and switch to SATA > IRST (Intel Rapid Storage) but it of course made zero difference. So I switched SATA back to AHCI

    Beyond this, I'm at a loss to explain this. This is baffling to me. There has got to be some setting somewhere in 20H2 that is managing or throttling the HDD speeds. My Win 10 Pro installs are standard MS sourced ISO's. I'm not using any of the new funky slipstreamed OS's that are popular right now.

    What setting is enabled by default in 20H2, that isn't enabled in 1909, that would account for these avge 40% + speed drops (up to 80% sometimes) on my Bitlocker enabled HDD's?
    Last edited by SaFrank; 12 Apr 2021 at 18:51.
      My Computer


  2. Posts : 5,816
    Win 11 Pro (x64) 21H2
       #2

    SaFrank said:
    What would cause a considerable speed difference between Bitlocker enabled HDD's in Win 10 Pro 1909 (18363.1440) and Win 10 Pro 20H2 (19042.867).
    Honestly it could be anything from code changes to hardware to when the tests was run.
      My Computers


  3. Posts : 494
    Win 10 Pro x64 versions
       #3

    I am not a Bitlocker expert by any means but is this were me I would remove the encryption completely from all the drives. Then I would shutdown the computer using an Admin command prompt Shutdown /s command. After shutdown start up the PC again and once Windows is fully booted and all apps are started and the system is stable I would then go about restoring Bitlocker to all drives beginning with the OS NVMe drive.

    After that run a few tests and see what your results are.
      My Computer


  4. Posts : 5,816
    Win 11 Pro (x64) 21H2
       #4

    Railtech said:
    I am not a Bitlocker expert by any means but is this were me I would remove the encryption completely from all the drives. ....

    That may not make a difference since a BitLockered drives do incur a small performance hit....

    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.
    Source: BitLocker frequently asked questions (FAQ)

    That said, I still use it (using it now) without hesitation or reservation. The security it provides is worth the small performance hit (to me).
      My Computers


  5. Posts : 494
    Win 10 Pro x64 versions
       #5

    My suggestion has nothing to do with not using Bitlocker rather, it is to reset the Bitlocker processes so that all is new rather than possibly have some only garbage hanging around.

    Theory - when you performed your fresh install of 20H2 your OS disk would be assigned a new disk signature. Now I don't know if the disk signature effects how Bitlocker operates or not but let's say it does. If disk signature changes and Bitlocker after your upgrade finds this new signature might certainly cause issues with encryption behavior. Starting fresh then may fix such an issue. Besides a difference in signature there are likely differences in metadata between the disk old install and a new install on a cleaned drive.

    Up to you though, you can live with it or try something simple to possibly fix it. You might want to look at the link below as by now you probably think I'm nuts.

    BitLocker Disk Encryption - Forensics Wiki
      My Computer


  6. Posts : 5,816
    Win 11 Pro (x64) 21H2
       #6

    Railtech said:
    My suggestion has nothing to do with not using Bitlocker rather, it is to reset the Bitlocker processes so that all is new rather than possibly have some only garbage hanging around.
    Your suggestion has everything to do with BitLocker as explained.... a performance hit; which is what the OP is noticing.

    And the FAQ link is direct from Microsoft which also has side links for everything BitLocker

    All said, I'm not saying the OP shouldn't try your suggestion (It "could" improve things), I'm saying there will still be a performance hit with BitLocker enabled.

    Peace
      My Computers


  7. Posts : 494
    Win 10 Pro x64 versions
       #7

    I agree, there is going to be a performance hit with Bitlocker no question on that. To see a heavy hit on performance is something to be looked into which is what I read here. Guess we will see if the OP posts back.
      My Computer


  8. Posts : 5,816
    Win 11 Pro (x64) 21H2
       #8

    I don't think your suggestion was fully off base; it just didn't account for BitLocker being a performance hit.

    What the OP could do (time consuming though as the files will need to be fully decrypted) is remove BitLocker and try running the benchmarks a day or two later to see what those numbers are and compare to what's posted here.

    Also double check they have the lasted motherboard chipset drivers (and drivers in general). And as a reminder, HDD drives are not SSD's so those numbers are not going there.

    I don't have any HDD's in my system so I can't post a comparison. I will note my NVMe SSD numbers for my OS drive aren't where they should be with BitLocker enabled. My other NVMe drive without BitLocker is about 4 percent faster overall.
      My Computers


  9. Posts : 4
    Win 10 Pro 1909 (18363.1440) and 20H2 (19042.867).
    Thread Starter
       #9

    Railtech said:
    I am not a Bitlocker expert by any means but is this were me I would remove the encryption completely from all the drives. Then I would shutdown the computer using an Admin command prompt Shutdown /s command. After shutdown start up the PC again and once Windows is fully booted and all apps are started and the system is stable I would then go about restoring Bitlocker to all drives beginning with the OS NVMe drive.

    After that run a few tests and see what your results are.
    Even before you posted this I had similar ideas about ways of testing this.

    I've been using Bitlocker for years on multiple systems; currently 2 PC builds and one laptop. I'm floating nearly 20 drives (HDD's, SSD's, and one NVMe) all except one has Bitlocker enabled. So I have at least some experienced and reasonable expectations of what to expect in terms of performance hit. Generally it's only about a 5% hit between Bitlocker enabled / disabled ... maybe 8% max.

    The point I was trying to make with the OP wasn't whether Bitlocker incurs a performance hit, but that I was seeing a major difference in said performance hit between Bitlocker encrypted drives in Win 10 1909 and Win 10 20H2. Perhaps my post wasn't clear, but that's the salient point here. I'm not blaming that OS either btw, just reporting observations.

    I have since replicated the exact same problem on a 2nd build (i7 4790 / Z87 mobo / OS on 860 EVO SSD / 2 TB Black HDD) The Bitlocker encrypted 2 TB Black HDD speed on that build also tanked by roughly 40%, between OS 1909 and a fresh install of 20H2.

    So I was thinking along the same lines as Railtech. I decrypted that 2 TB yesterday speeds were back up in the normalish 150 - 160 MB /s. range

    Because decrypting ~ 20 drives (some 6 - 8 TB backups) would take considerable time, I am going to diskpart clean a few drives. Not because diskpart is a magical solution, but because it will be quicker to do that to remove Bitlocker and wipe the drive. (Decrypting the 2 TB Black with about 420 GB, roughly 25 % full, took nearly three hours. So ya do the math on 20 drives) Half the drives are backups. I have data in cloud backups also. So I lose nothing by trying that on at least one or two drives.

    I have not re-encrypted the aforementioned 2 TB Black yet because I'm using MSMGToolkit o create a slipstreamed 20H2 install with a lot of junk stripped out.
    MSMG Toolkit

    Another test. Then I'll install as a test on build # 2.

    But one way or another, all the drives will either be de-encrypted, or clean / reformatted and I'll encrypt again under the new OS.

    Then I'll report back and let you know if that has made a difference. But this is gong to take some time.
      My Computer


  10. Posts : 494
    Win 10 Pro x64 versions
       #10

    Understand completely, looking forward to your report back. Being a storage disk subsystem junkie myself, I'm curious to know the outcome.
      My Computer


 

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