Very bad 4K read speed with Sandisk SSD Plus 240GB, any idea why?

[hubbybenjamin]

I replace the harddisk with Sandisk SSD Plus 240GB which I bought few days ago in my old samsung notebook NP350V5C. The notebook is running windows 10 Home 64 Bits version and the SSD is running in SATA 3. I have tried to use the Microsoft chipset driver, turn off the Windows Write-Cache Buffer Flushing, run windows safe mode, run in high performance mode, check partitions are correctly aligned. The CrystalDiskMark score pic is attached. Any idea why the 4K read speed is so low? Thanks.

 

[USAFRet]

This is my Sansdisk Ultra II 960 GB.

The only thing that jumps out at me for your drive is the lack of free space. 8% is not enough.

 

[hubbybenjamin]

This is my Sansdisk Ultra II 960 GB.

The only thing that jumps out at me for your drive is the lack of free space. 8% is not enough.

I saw many different options about this. The size should be 256GB so there is already 16GB as reserved space, something 5% to 10% should be enough, at least not affecting speed much.

 

[USAFRet]

Have you run whatever diagnostics Sandisk has?

 

[hubbybenjamin]

Have you run whatever diagnostics Sandisk has?

yeah, actually I saw people discussion in other posts, this Scandisk model has different version, and latest version has real "cheap shot" and the 4k performance is actually this bad. Look like WD really wants to have big profit.