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.

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**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

[niegowic]

Before upgrading IOPS dropped by half... 

[Memory Product Expert -1]

Hello niegowic,

Are you able to post screenshots of your performance test results and your system specs?

If you are having an issue, make sure to post all important information showing the problem and why you think this issue is caused by the firmware. Also, make sure you are using the product using the recommended settings and Operating system. 

Otherwise, no one will be able to help or investigate the issue...

[Memory Product Expert -1]

Here are my performance results as of this morning, for reference 

 

 

[SFdrifter]

Ok...I may have created a tempest in a teapot, but I think I have a better sense of what’s happening. Whether it’s by design or a bug, I’m not sure. Let me focus on the random write issue.

First, apologies to Memory Product Expert -1 -- after reviewing all my benchmark data since April, I don’t think what I’m seeing is tied to the new firmware – I’ve been seeing poor random write performance all along. It just coincidentally happened that my benchmark using the 4B2QJXD7 firmware immediately before updating to the 7B2QJXD7 firmware had exceptionally good results for the 2TB drive, and my initial post was prompted by the difference in performance that I saw.

Second, the parameters I’ve been using in fio testing have a large part to play. I’ve previously tested random write performance using this command (call it the “sustained random write” test):

fio --name=write_iops_random --directory=”$TEST_DIR” \

--numjobs=2 --size=10G --time_based --runtime=60s --ramp_time=2s \

--ioengine=libaio --direct=1 --verify=0 --bs=4K --iodepth=32 \

--rw=randwrite –group_reporting=1

For the 990 Pro 4TB drive, average random write speeds for both firmware versions ranged from ~1,100k to ~1,300k IOPS. For the 990 Pro 2TB drive, average random write speeds ranged from ~350k to ~600k IOPS (with the one outlier of ~1,392k IOPS). These results were consistent across both firmware revs (notwithstanding the outlier).

I noticed, however, that, for the 2TB results, the avg IOPS might be significantly below spec, but fio also (but not always) reported max values of ~1,380k IOPS, indicating that the SSD hardware is capable of fast random writes approaching the spec value.

When I modified the above fio command by changing the runtime to 5s and ramp_time to 1s (call it the “burst random write” test), the results changed markedly:

For the 990 Pro 4TB drive, the avg random write speed was 1,391k IOPS; for the 990 Pro 2TB drive, the avg random write speed was 1,393k IOPS. Increasing the runtime to 10s (and ramp_time back to 2s), and the 2TB avg random write speed again dropped significantly below spec to 599k IOPS.

So, here’s what I infer from these results:

** there’s nothing wrong with the 2TB drive hardware.

** the 2TB drive’s SLC cache is being exhausted sooner than that of the 4TB drive – either it’s physically smaller or the drive’s ~50-60% utilization has reduced its capacity. Or the 2TB firmware’s write management is not the same as the 4TB’s: background operations start during sustained random write, garbage collection begins, and write amplification increases, all leading to lower average random write speeds.

** cache state affects the fio testing, causing the range in avg random write speeds that I’ve seen in the 2TB drive

** the 4TB drive might be performing better during the sustained random write test because it has more NAND chips and better heat distribution, because it has more parallel NAND channels, and/or because its firmware handles write management better.

Or something else entirely.

So, what’s the bottom line?

**I don’t think the 7B2QJXD7 firmware caused any degradation in performance that wasn’t already present in earlier firmware;

**burst random write performance of the 990 Pro 2TB drive over 5 seconds roughly meets the spec’ed value (or at least isn’t egregiously lower);

**sustained random write performance of the 990 Pro 2TB drive over 10 seconds or more drops to ~25% of spec, but the worst value I saw (375k IOPS) is still significantly better than the SATA 870 EVO drives I tested or than a hard drive.

**the difference I reported earlier in the Power On Hours from “smartctl -x” for the two drives is still a mystery – if it’s correct, then what’s going on?

What do you think?

[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.

[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?