I have 240GB Lexar NQ100 SSD in my old laptop (max read/write speed 500MB/s), split in two 100GB partitions, first partition is OS Windows 7 other empty so far.

I have copied 40GB of files one big 25gb other small from one partition to another and my copy speed started first at 300 MB/s then 100 MB/s an then ended at regular 30 MB/s and my whole system lag i could not open Firefox took ages to load and my DPC latency had some red spikes (DPC Latency Checker).

As soon as copy finished system worked good once again, it even felt like programs that are already loaded were not working properly like Firefox could not connect to internet and overall system lagged even though CPU use was low and plenty of RAM.

Here's another latency checker tool. enter image description here

My SSD is aligned using AOMEI Parition Assistant

So my question is why i get such a degraded performance out of my SSD, even worse than regular HDD would give me while copy speeds are very low as well.

Was it SSD issue or storage controller issue or driver issue, what test procedure i can preform to find out what exactly is causing this lag?

Edit: Benchmark.

enter image description here

1 Answer 1


Ive never used that drive, but I'd put my money on it being limitations on the drive. There seem to be a few things at play here -

This is a very entry level drive, and while it claims 500MB+ read speeds, it does not appear to claim write speeds (at least not that I can find) - these are drastically slower - see https://www.storagereview.com/review/lexar-nq100-ssd-review and https://nikktech.com/main/articles/pc-hardware/storage/solid-state-drives/12117-lexar-nq100-960gb-ssd-review?showall=1 for some performance tests.

Importantly, the drive lacks DRAM - this means it's going to be a lot slower for heavy writes, and have a very low TBW (terabytes written - 84TB) which indicates a short lifetime in a write heavy environment.

You may want to get Crystal Disk Info or similar and look at the state of the drive (i.e. its S.M.A.R.T values). My guess is it is getting older and slowing down. SSDs - especially small cheap ones like this - can get drastically slower than HDDs as they age, and that's likely happening here (even though the drive is not that old!) I saw this behaviour on early 128GB Intel drives and was quite surprised at the time. It likely has to do with poor wear levelling algorithms in the firmware.

Crystal Disk also have a free benchmark program which can also report on drive speeds which you may want to try ad well.

  • 1
    I figured it was my the fact that SSD was split into two partitions 100GB each and first partition was like 90% full. So my write speed fall to about 30MB/s i deleted additional files and merged partitions into one now speeds improved back to stock speed see screenshot in original post. Mar 17, 2022 at 17:54
  • Well done. You should post this as an answer and unaccept my answer and accept this.
    – davidgo
    Mar 17, 2022 at 17:59

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