Potential bug with AS SSD Benchmark and NVMe drives?

Hello,

There's been some recent debate regarding the performance of Toshiba's XG4 NVMe SSD which is included on the new HP Spectre x360 (13 and 15 inch models) as well as Dell XPS notebooks. See here for some discussion: https://www.reddit.com/r/Dell/comments/5xvrvi/howto_95605520_toshiba_ssd_optimizing_performance/

Basically, people are getting either a Samsung PM951, Samsung PM961, or Toshiba XG4 SSD. The issue is, while the results with the Toshiba appear fine on CrystalDiskMark, the write speeds on AS SSD Benchmark appear terribly slow. People have had success raising their scores after installing an OCZ RD400 driver, but I'm wondering if the issue is truly with the Toshiba drive or AS SSD itself.

Has anyone noticed an issue with very slow write speeds on their NVMe when testing with AS SSD vs CrystalDiskMark?

While the issue has been centered around the Toshiba drive, as seen in the thread mentioned above, I have two HP Spectre x360 laptops, one with the Toshiba XG4 (THNSN5512GPUK) and one with Samsung PM951 (MZVLV512) and so I ran CrystalDiskMark and AS SSD on both tonight. I've attached all 4 scores. It appears that the poor write speeds with AS SSD affect the Samsung SSD as well. If that is the case, isn't this more reason to believe that the issue is with AS SSD and not Toshiba's driver? http://imgur.com/a/axFAH

The issue also occurred with the HP Spectre x360 15 test unit on notebookcheck's review. See "Storage Devices" under this review for the benchmark and note regarding the AS SSD bug: http://www.notebookcheck.net/HP-Spectre-x360-15-bl002xx-Convertible-Review.196694.0.html (Note: there is a typo where they call it the XG3, but it is the XG4 according to the photo and model number)

It appears to have happened with a Lenovo as well: https://forums.lenovo.com/t5/ThinkP...Very-slow-SSD-write-speeds/m-p/3399071#M71875

In day to day use, my computer has been very speedy, but I want to make sure I'm getting the proper speed out of my hardware.

Any thoughts on this would be greatly appreciated.

My specs: HP Spectre x360 13-ac076nr Windows 10 Home 64 7th Generation Intel® Core™ i7 processor (i7-7500U) 16 GB memory; 512 GB SSD storage 13.3" diagonal Full HD touch display Intel® HD Graphics 620

 

For those still curious, it appears the issue is related to FUA (Forced Unit Access). PCWorld explains it as well under "Testing oddities and revelations" here: http://www.pcworld.com/article/3133753/storage/plextor-m8pe-nvme-ssd-looks-fast-is-fast.html

I received a message back from one of the editors at PC World regarding this. He states "What those Toshiba/Samsung drivers do is simply ignore the FUA commands, leaving the cache functional. This gives you better test results under AS SSD. In real life, the FUA command is rarely if ever used, so the driver is of little benefit. FUA is largely for servers. Your understanding is correct. Basically you will get the same real life performance either way."

A Lenovo engineer also mentioned: "The problem is that the AS SSD Benchmark is issuing commands with the caching set for Write Through instead of Write Back mode. The RSTe driver sets a command bit called "Force Unit Access" (FUA), which disables the drive's on-board cache, which is causing the low write performance numbers. Windows operations are done in Write Back cache mode so AS SSD’s benchmark is not indicative of actual Windows system performance. We saw this issue with Crystal Disk Mark (another storage performance benchmark) and they fixed it with Crystal Disk Mark 5.02. My recommendation is to try the Crystal Disk Mark 5.02 benchmark and compare the performance using that tool instead."

 

I am wondering why the AS SSD Benchmark is so slow on my drive and taking very long time (see the 10:37 remaining time for that 4k write test alone) until i have to abort the test, apparently this is the reason.


With Crystal Disk Mark it seems to be ok.

 

Try installing Samsung Controller driver and see whether it makes any difference.

 

That would require me to switch to AHCI in bios, Samsung driver does not install under RST. Will try that when got free time.