Samsung 990 PRO 2TB: Performance Degradation After 7B2QJXD7 Firmware Upgrade - Capacity-Specific Bug?

[SFdrifter]

PLEASE NOTE THAT THIS FIRST POST WAS MOSTLY INCORRECT -- I MISINTERPRETED SLC CACHE EXHAUSTION FOR POOR PERFORMANCE; I DO NOT BELIEVE THERE IS A FIRMWARE BUG INVOLVED

I'm reporting an apparently capacity-specific firmware bug affecting Samsung 990 PRO 2TB drives after updating to firmware 7B2QJXD7. My 4TB 990 PRO with identical firmware performs normally.

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**AFFECTED DRIVE:**
- Model: Samsung SSD 990 PRO with Heatsink 2TB (used as system drive with 5 partitions)
- Serial: S7DRNJ0XC08579H
- Firmware: 7B2QJXD7 (upgraded from 4B2QJXD7)
- System: Arch Linux, AMD Ryzen 9 9900X

**COMPARISON DRIVE (NORMAL):**
- Model: Samsung SSD 990 PRO 4TB (used as data drive with 1 partition)
- Serial: S7DSNJ0X912378T
- Firmware: 7B2QJXD7 (upgraded simultaneously with the 2TB SSD)

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**PERFORMANCE DEGRADATION (FIO BENCHMARKS):**

**2TB Drive - BEFORE firmware upgrade, using 4B2QJXD7:**
✓ Sequential Write: 6,650 MB/s
✓ Random Write: 4,436 MB/s (1,135K IOPS)
✓ Sequential Read: 6,650 MB/s
✓ Random Read: 2,970 MB/s (760K IOPS)

**2TB Drive - AFTER firmware upgrade, using 7B2QJXD7:**
xx  Sequential Write: 1,478-3,691 MB/s (45-78% LOSS)
xx  Random Write: 1,375-1,460 MB/s (68-70% LOSS) ← CRITICAL
✓  Sequential Read: 6,752-7,007 MB/s (normal)
xx  Random Read: 2,369-2,582 MB/s (13-20% loss)

**4TB Drive - AFTER firmware 7B2QJXD7:**
✓ Sequential Write: 6,577 MB/s (NORMAL)
✓ Random Write: 4,435 MB/s (NORMAL - matches 2TB baseline!)
✓ Sequential Read: 6,687 MB/s (NORMAL)
✓ Random Read: 4,594 MB/s (EXCELLENT - better than 2TB baseline!)

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**TESTING METHODOLOGY:**

To isolate the issue, I performed extensive testing:

1. Tested across multiple partitions (root, home, data)
2. Tested from Live USB (eliminating OS activity)
3. Tested both drives with identical parameters
4. Monitored temperatures during tests

**KEY FINDINGS:**
- Performance degradation occurs on ALL partitions of 2TB drive
- Live USB testing (no OS) still shows degraded performance
- 2TB drive runs 26°F hotter than 4TB (113°F vs 87°F)
- Higher temp suggests excessive write amplification?
- 4TB drive with SAME firmware performs perfectly
- Both drives updated simultaneously
- Both have similar write endurance (~22-23TB)

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**TEMPERATURE COMPARISON:**
- 2TB (Problem): 113°F / 45°C (elevated)
- 4TB (Normal): 87°F / 31°C (normal)

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**POSSIBLE IMPLICATIONS**

Is this a **capacity-specific firmware regression** affecting 2TB 990 PRO models?  Does the 7B2QJXD7 firmware have different code paths for different capacities, and does the 2TB implementation have a critical bug in random I/O handling?

The elevated temperature on the 2TB drive suggests the firmware is causing excessive internal operations (write amplification, garbage collection, etc.).

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Dear Samsung -- 

1. Can you please confirm this capacity-specific bug?
2. Can you investigate why 2TB apparently differs from 4TB implementation?
3. Can you provide a firmware fix (8B2QJXD7) or rollback capability?
4. Can you provide guidance for affected users?

**Has anyone else experienced this after updating 2TB 990 PRO to 7B2QJXD7?**

I have detailed benchmark logs, SMART data, and test results available as requested.

---

**System Details:**
- OS: Arch Linux (kernel 6.x)
- Motherboard: AsRock x870e Taichi
- Testing Tool: fio 3.39
- Test Parameters: libaio, direct I/O, various block sizes

[Memory Product Expert -1]

Hello SFdrifter 

Thanks putting this information here as it helps clear up misconceptions for other users,

In my honest opinion, it does sound like it could be a cache issue or worst case some kind of drive specific controller issue possibly with that drive, 

but, How long have you had this 990 PRO 2TB?
Could it be a pcie power issue with motherboard?

[SFdrifter]

I hesitate to even conjecture...how would I be able to test the M2_1 slot of my motherboard to know that it's OK?  That might explain why the 4TB in a different slot performs so differently and might even explain the Power On Hours discrepancy...but, then again, it might not.  If you have a recommendation for testing the slot, let me know.  I could swap the 2TB and 4TB drives and repeat the benchmarking, but I'm not confident that would prove anything.  Otherwise, I bought the 2TB and 4TB 990 Pro's (and the X870e Taichi motherboard) in February 2025.

Following up, I found a review of the 990 Pro 2TB that does a very good job of explaining SLC impact on benchmarking metrics.  My changing the fio runtime parameter is equivalent to looking at performance with different amounts of data written, as discussed in the review; effectively, I'm seeing performance either before or after the SLC cache is exhausted.

Here's the link:  https://www.techpowerup.com/review/samsung-990-pro-2-tb/

[Memory Product Expert -1]

Hello SFdrifter, 

Does the motherboard manufacturer have a diagnostic tool available?
Changing the slots might also show a difference and if this difference is consistent, this could potentially give you a new lead
Also Not sure if the OS, would be a factor but Windows does have power management options which in a lot of cases its best to set it to a manual mode instead of auto, too make sure the OS isn't making any bad decisions in the background in order to "save" system resources.

I believe even the Samsung Magician software has a full performance mode which I think also maximizes the power management for Windows. 

[SFdrifter]

I'll be honest...I've kind of enjoyed benchmarking and beginning to understand how the variable size SLC cache affects results, but I've come to the conclusion that what I was seeing (except for the different Power On Hours between the 2TB and 4TB Pro's -- that's a puzzler!) is due to the design of the 2TB HW & FW and the size of the SLC cache with ~57% utilization.

If the M2_1 slot really was an issue, I would expect to see throttling under high-load scenarios, both poor burst and sustained performance, lower sequential write speeds, more system errors or drive disconnects (although I did suffer ~25 system crashes since the February build, but the  7B2QJXD7 firmware is supposed to directly address that issue), and, maybe thermal throttling alerts.  So, yeah, I'm not going to swap the 2TB and 4TB drives -- my new NVMe Gen5 system drive should be arriving shortly, and that's enough swapping for me.

Interesting to note, though:  the M2_1 slot of the AsRock X870E Taichi is the only slot to support PCIe 5.0 and the only slot that is direct-to-CPU.  Unfortunately, the motherboard design routes some heat through the slot and its heatsink, explaining why my 990 Pro 2TB consistently shows higher idle temps than the 4TB (typically 40-50C vs 30-40C):  https://www.reddit.com/r/ASRock/comments/1ha3c9j/comment/mva0zow/  But, even so, I've never measured temperatures beyond ~68C on the 990 Pro 2TB during benchmarking, and smartctl shows no critical temp events.

Thanks for helping me better understand the issues here; again, apologies for raising a fuss over something that is likely by design.

[Memory Product Expert -1]

Hello SFdrifter ,

Does anyone have result performance before and after firmware update? I personally still don't see how the low random write is caused specifically by firmware and nothing else ?

It seems like everyone is pointing the issue towards the firmware, solely based on the fact that the firmware was the last thing that changed. 

But i posted my performance on page 1 of this thread, I have the latest firmware 7B2QJXD7, My drive is also 2TB and I am not seeing the same issue. 

[SFdrifter]

"Does anyone have result performance before and after firmware update?"  Well, one can only hope so.  The difficulty, of course, is that, to my knowledge, there's no way to rollback the firmware version, so there's no way to readily repeat the experiment.

"It seems like everyone is pointing the issue towards the firmware, solely based on the fact that the firmware was the last thing that changed."  Fair enough, but, hey, isn't that the scientific method?

"I am not seeing the same issue."  I understand -- although how much of the drive's capacity is used may also play a part (in my case, it's my system drive with 5 partitions, and total usage is ~55%).  Unfortunately, I'm using Linux, so I can't use Samsung Magician to assess performance -- another variable in assessing this issue.

I repeated my initial post on Anandtech, trying to drum up more data.  My most recent post there provides a little more data as well as the fio commands that I'm using (see https://forums.anandtech.com/threads/samsung-990-pro-2tb-performance-degradation-after-7b2qjxd7-firm...).

Note that the degradation in random write performance that I'm measuring isn't really perceptible -- if I weren't benchmarking after each major change, I wouldn't have noticed anything different.

[e-thanos]

I got the same issues since I did the update yesterday on my two 2Tb 990 pro drives.

I will never trust Samsung EVER AGAIN.

Both drives go 6 degrees Celsius up and performance is degraded.

[Memory Product Expert -1]

Hello e-thanos ,

I think its best that you read the information in this thread carefully,

What do you mean by "performance is degraded"? Can you post pictures to show your slow performance? 

also, 6 degrees Celsius difference is not a problem, can you post pictures of your temperature currently? 

[ebutusov]

Hi,

I found similar issue with my recent build. There are 3 990 Pro drives, 2x2TB and 1x4TB. I bought them at almost the same time, the were brand new and sealed. I installed them on December 2025 at the same day. After 2 weeks or so I discovered abnormal TBW on system drive (2TB capacity) - it was around 1TB, while total amount of data on the drive was around 200GB. I couldn't find the explanation for this - I installed OS (Win 11 Pro) and a couple of apps, but nowhere near 1TB in total. Then I realized that drives have different power on hours count. The system (C: drive, the 2TB one) showed 240 hours, while other two (2TB and 4TB) had 140 hours. I couldn't explain that also - I put them into my motherboard at the same time. What is interesting is that power cycle count seems to be consistent - all drives show the same value. Then I started the observation of C drive TBW. After a couple of days I found out that it increased by 70GB in ONE DAY just out of the blue, without any significant writes from the OS. I started to looking up for similar cases and found this post.

The details (from HWinfo):

C (2TB 990 Pro) - OS drive
----------------
Drive Firmware Revision: 8B2QJXD7
Device Health: 100%
Power Cycles: 54
Power On Hours: 398 hours
Unsafe Shutdowns: 1
Total Host Writes: 1.56 TBytes

D (2TB 990 Pro)
-----------------
Drive Firmware Revision: 8B2QJXD7
Device Health: 100%
Power Cycles: 54
Power On Hours: 205 hours
Unsafe Shutdowns: 1
Total Host Writes: 1.07 TBytes

E (4TB 990 Pro)
------------------
Drive Firmware Revision: 8B2QJXD7
Device Health: 100%
Power Cycles: 54
Power On Hours: 203 hours
Unsafe Shutdowns: 1
Total Host Writes: 1.20 TBytes

The only visible difference between the drives is that C (OS drive 2TB) is made in Vietmam, while other two are from Korea.
As you can see the Power On Hours is still incorrect and the difference is now even bigger. I guess there is a bug in power on hour calculation, and some aggressive house keeping is going on - because how could we explain such a large amount of data written just out of nowhere?

I haven't noticed any performance downgrade - all the drives have almost the same results in Samsung Magician, with 4TB being slightly better (around 10%) in random writes.

Hope there is some explanation to the strange counter values in TBW and Power On Hours.

Regards,