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M8PE extremely slow writes

Concillian

Diamond Member
May 26, 2004
3,755
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Reaching a dead end trying to figure out the issue with this system.

Brand new fresh install of Win10 Home.

Plextor M8PEg 512GB in the M.2 slot
Mushkin Reactor 1TB on a SATA

Both SSDs new for this system.

The Reactor runs AS SSD normally, and gets benchmarks you'd normally expect for it.
Seq r / w = ~500 / 400 MB/s
4k = ~30 / 100 MB/s
4k-64 = ~270 / 240 MB/s
access = 0.035 / 0.045 ms

overall pretty normal.

But the M8PE is showing abysmally low random write performance:
Seq r/w = ~800 / 250 MB/s
4k = ~35 / 2.8 (yes, 2.8) MB/s
4k-64 = ~167 / 5.5 MB/s
access = 0.33 / 1.55 ms

It's not just a little bit low, something is not right at all, and I can't seem to figure it out. There's no BIOS options I could find in the BIOS (MSI Z97 Gaming 5 board with a 4770k) pertaining to the M.2 configuration. AS SSD does show the driver as the NVMe driver (stornvme). Install is literally a fresh install, install drivers, perform windows update and then benchmark. Nothing else on the system.

Anyone have any ideas?
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
13,687
4,282
146
Are you running the latest BIOS on your motherboard?

Also, there was a firmware update from Plextor for that drive. Have you done that?
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
13,687
4,282
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Also, I just looked and it appears your motherboard doesn't have a PCIe 3.0 x4 M.2 slot. On the product page it states its M.2 slot supports PCIe module up to 10 Gb/s. The newest slots offer up to 32 Gb/s.

https://us.msi.com/Motherboard/Z97-GAMING-5.html#hero-overview

http://www.tomshardware.com/answers/id-2986465/msi-z97-ganming-nand-ssd-950-pro.html

I also found this previous help thread where they have your MSI motherboard and have slow performance after adding a NVMe drive:

https://forums.anandtech.com/threads/bought-a-samsung-950-pro-m-2-and-cant-get-it-to-work.2453698/

It looks like you will need to use an adapter card to get the full performance out of your drive.
 
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Concillian

Diamond Member
May 26, 2004
3,755
8
81
Yeah. the M.2 slot is not full x4 speed. I know this.

That's not the issue.

Look at the 4k random writes... 2.8 MB/s? My SATA SSD is almost 50 times faster. The slot is not full x4 speed, but it should still be quite a bit faster than a middle of the road SATA SSD.

We aren't talking about an issue where speed is a little slow, Guru3d AS SSD shows 640 MB/s write in 4k-64 and mine is 5.5... It should be over 100 times faster than it is... two orders of magnitude slow.

The guy you linked was getting 950ish MB/s sequential read and write, which I'd be happy with. That tells me that the slot should be capable of better than SATA write performance, but I'm abysmally low.

Yes, drivers and BIOS are up do date. I'll check out the Plextor firmware (Edit: Just checked... Firmware is v1.04, which is the latest listed on Plextor's site.)
 
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XavierMace

Diamond Member
Apr 20, 2013
4,307
444
126
2ms access time is also rather high for an SSD. Can you "borrow" another M.2 to compare to?
 

UsandThem

Elite Member
Super Moderator
May 4, 2000
13,687
4,282
146
Yeah. the M.2 slot is not full x4 speed. I know this.

That's not the issue.

Look at the 4k random writes... 2.8 MB/s? My SATA SSD is almost 50 times faster.
Send a message to Plextor and MSI tech support.
 

Concillian

Diamond Member
May 26, 2004
3,755
8
81
2ms access time is also rather high for an SSD. Can you "borrow" another M.2 to compare to?
No but I have another machine with the same board. I was going to wipe it and try it as a non-boot drive on that machine and see if anything is different.
 

Billy Tallis

Senior member
Aug 4, 2015
237
99
101
At least part of what you're seeing is a known issue with Microsoft's NVMe drivers: they're more cautious about letting the drive buffer writes than their AHCI/SATA drivers are. This only has a significant impact on applications that try to bypass the file system's cache in main DRAM. In other words, benchmark tools and transactional databases are affected, but most ordinary software isn't. You can change the NVMe SSD's write cache buffer flushing setting in order to get behavior that is approximately equivalent to how SATA drives are treated by the OS, but it still isn't a true apples to apples comparison.
 

Concillian

Diamond Member
May 26, 2004
3,755
8
81
It was the buffer flushing thing. After turning that off, it benchmarks as I would have expected. Faster than my SATA drive, but not as fast as reviews because the z97 m.2 bandwidth is not full x4 PCIe. I will turn it back on for normal operation, but at least I know now that nothing is obviously wrong and can continue on with the build to overclocking and stability testing.

Thanks.
 

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