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

sygnus21 said:

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.

Yes, that's pretty much what I'm doing.

sygnus21 said:

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 thought about that regarding motherboard drivers, but I haven't done that because on the main build with the Gigabyte Z390 Master motherboard, I didn't see anything from Gigabyte that I though would be better that what current Win 10 installs provide.

For example, here's the driver page for the Z390 Master

Z390 AORUS MASTER (rev. 1.0) Support | Motherboard - GIGABYTE Canada

Under SATA RAID/AHCI I don't see anything that would benefit HDD's in AHCI mode. My thinking may be wrong but I thought the Intel SATA Preinstall driver would only be of benefit for RAID arrays. And the IRST is for IRST mode which I don't use.
Do you see any there you would use?

Regarding BIOS something that I did consider was BIOS version. I'm running F8 which is older for that mobo. Newest is up to V F11. But because version notes mention nothing about optimizations for OS's I didn't think that was necessary.
Would you consider updating BIOS version also?

Hi

I am so happy someone has finally stumbled onto the same issue I noticed last year. I decided not to try and log it as a support issue as no one else had posted anything about it on the internet and the thought of trying to get Microsoft to deal with it as a support issue filled me with dread as history has shown they will point the finger at everyone else to fix.

I am using 1TB Samsung 970 Evo Plus NVME drives in 2 similar computers. I was consistently getting the expected 3500MB/s READ speeds in build 1909 of Windows 10 on both of them regardless of whether I had the drives encrypted with Bitlocker or not. This is what they should be doing.

When I installed Build 2004 early last year I noticed that the read speeds dropped consistently to around 3000MB/s in any benchmarks I ran (Samsung Magician, CrystalDiskMark etc.) if I had bitlocker enabled. If I removed bitlocker or went back to Windows 10 build 1909 the read speeds reverted to 3500MB/s. This proved the issue was both with bitlocker and Windows 10 build after 1909. I tried on both machines and got exactly the same outcomes.

I tried Build 20H2 later in the year and the same happened. At this point I was 100% convinced Microsoft had changed something in bitlocker in builds after 1909. What I couldn't establish is whether the benchmarks were reporting incorrectly or whether I was really getting a near 20% drop in read performance.

I decided to restore back to a 1909 image and have been running it happily with 3500MB/s and bitlocker enabled. With the impending removal of support of 1909 I have installed Build 21H1 over the weekend and I can confirm the issue is still present.

Without Bitlocker



With Bitlocker

sygnus21 said:

BitLocker will imposes a small penalty hit when in use....



Source: BitLocker FAQ - Is there a noticeable performance impact when BitLocker is enabled on a computer?

Your hit seems to be about a 1.16% percentage hit

Hi. Not sure where you got 1.16% from in my graphics. In fact I'm really lucky Bitlocker has no impact on performance when running Windows 10 Build 1909 from my tests. The issue being raised on this thread by the original author and by me is that all subsequent builds of Windows 10 after 1909 have a 15%-20% hit on performance which is massive. Read times are now at 3000MB/s as opposed to 3500MB/s.

Hi,

Pinging this thread as I am also happy to finally have found a place (and surprisingly the only place) where the issue I am experiencing is being discussed.

It took me years since the release of 20H1 to finally have tracked back the issue to bitlocker and this thread. Back in 2020 I decided to delay upgrading Windows writing up the issue to my hardware configuration at the time thinking I had some unique problem affecting file copy speed.

Fast forward to today I have built a completely new system on Windows 11 and lo and behold I am seeing file copy speeds dropping on hard drives compared to the speeds they were operating at under 1909.

For a long time I didn't realize Bitlocker was a factor as all my storage is encrypted by it. I tried clean reinstalls, new SATA cables, different drives, different copy modes to no avail, my issue is the same as being discussed here:

In a realworld file copy scenario after about 10 GB of file transfer completing at regular speed, file copy speed tanks by 30-40%, regardless of what is being copied (mix of 1-2 GiB files, 3-9 GiB or files well above 10 GiB), if I pause the copy and resume in a few seconds, copy speed recovers then starts to dip again. 10 GiB is well above buffer and cache sizes, I can hear spinning discs writing so it is not a cache issue.

Initially I thought the issue has to do with spinning disks as I had 3 SSDs in the system and the 2 SATA ones consistently saturated SATA bandwidth (~500 MiB/s) to days on end and the NVMe speed I never noticed since I didn't have 2 NVMe drives to copy between.

The penny dropped eventually when out of desperation I tried a new drive unencrypted and saw that the speeds I was getting unencryped in Windows 11 was the same as Windows 10 1909, then when I encrypted it immediately showed symptoms.

Bitlocker being a hit compared to no Bitlocker is something I can accept, even with a modern system I could understand that IOPS is affected and maybe to some extent copy speed too, but not by 30-40% and not in a way that is a clear sign of any version above 1909 applying some sort of throttling.

I tried all available bitlocker encryption algorithms and all software encryption modes (AES 128, 256, CBC, XTS) are affected, the two SATA SSDs I have hardware encryption on and they are not affected, this made it especially hard for me to trace the issue to bitlocker.

My latest hard disks can do 250 MiB/s with bitlocker software encryption in 1909, I get a paltry 130 MiB/s sustained speed out of them in Windows 11. I no longer have the option to run 1909 on a daily basis as my new system has features only supported under Windows 11.

My current "workaround" if you can call it that is batching up all my copying tasks and booting into 1909 to carry out all of it.

Heya!

I subscribed just to post my findings on the subject.

Indeed Microsoft changed BitDefender after 1909.
Windows 10 1909 and prior would use the SSD's own hardware encryption (faster) when available, but, since some SSD manufacturers used/are using non-secure master passwords that can give you access to the file encryption keys, Microsoft has now since defaulted to software encryption.

From searches...
This change occured on September 24, 2019, in KB4516071.

The more you know (*insert flying star jingle*) :)

Cheers!