Samsung 950 Pro m.2 NVMe Slow Sequential Read

SPARTAN VI

Supreme [H]ardness
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Jun 12, 2004
Messages
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Built a buddy of mine a wicked gaming rig and it's about 99% dialed in, except for the Samsung 950 Pro has sequential read speeds that are about 1/3 where they should be (800MB/s vs. 2200MB/s). This is the 3rd time I've installed a m.2 SSD on a Skylake build this year, so I thought I was ahead of this problem by disabling CSM and setting up Win10 using GPT instead of MBR. I'm on the verge of returning the 950 Pro for a standard 2.5" SSD instead, but wanted to run this by the [H] community first.

Here are his specs:
CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor
CPU Cooler: Corsair H100i v2 70.7 CFM Liquid CPU Cooler
Motherboard: Asus MAXIMUS VIII HERO ATX LGA1151 Motherboard (BIOS v2202)
Video Card: ASUS GeForce GTX 1080 8GB ROG STRIX Graphics Card (STRIX-GTX1080-8G-GAMING)
Memory: Corsair Vengeance LED 32GB (4 x 8GB) DDR4-3200 Memory
Storage: Samsung 950 PRO 256GB M.2-2280 Solid State Drive
Storage: Western Digital Blue 3TB 3.5" 5400RPM Internal Hard Drive
Case: Phanteks Enthoo EVOLV ATX ATX Mid Tower Case
Power Supply: SeaSonic X Series 850W 80+ Gold Certified Fully-Modular ATX Power Supply
Wireless Network Adapter: Asus PCE-AC88 PCI-Express x1 802.11a/b/g/n/ac Wi-Fi Adapter

What I've tried so far (no particular order):
  • PCIe set to Gen 3. Note: Mobo manual doesn't specify how to toggle m.2 between SATA and PCIe modes.
  • BIOS update to 2202.
  • Installed NVMe driver.
  • Disabled CSM. Installed Win10 w/ GPT partitioning.
  • Formatted and reinstalled Win10 w/ GPT partitioning.
  • AS SSD Benchmark and Samsung Magician both report the sequential read is about 700-800MB/s and random read IOPS are about 80% as advertised. Oddly the sequential and random write speeds are very close to advertised speed.
 
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Absalom

Gawd
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Oct 3, 2007
Messages
905
Try removing the Wireless NIC and re-benching.

From what I've read about the Maximum VIII Hero, if the device inserted into the M.2 slot is PCIe capable then the bios will detect this and set the mode to PCIe accordingly (no manual override anyway). In any event, those seq. read speeds are still beyond what SATA is capable of, but as you stated, a fraction of Samsung's advertised speeds.

The only other theory I can come up with is that the M.2. slot shares bandwidth with the other "lesser" PCIe slots. The manual is very explicit about which PCIe slots "share" bandwidth, but it neither confirms nor denies the M.2 slot sharing with anything (except when in SATA mode).

Edit: In Magician, it should show the Link Speed and Link Width Current.
 
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SPARTAN VI

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I'll check that out tonight and report back. I did move the WiFi NIC to another PCIe slot, but I haven't tried running it without the NIC.
 

SPARTAN VI

Supreme [H]ardness
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I'll check that out tonight and report back. I did move the WiFi NIC to another PCIe slot, but I haven't tried running it without the NIC.

So it's definitely on PCIe, and this is what Samsung Magician shows:

Link Speed Cur: 8Gbps, Max: 8Gbps
Link Width Cur: x4, Max: x4
Bandwidth Cur: 32Gbps, Max: 32Gbps

What's really confusing is I stopped by to check on the machine today, ran Magician and AS SSD, both benchmarks came back with the correct figures! Rebooted the machine to make sure it was OK, and it reverted right back to 1/3 speeds. Disconnecting the WiFi NIC had no effect.
 
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arestavo

[H]ard|Gawd
Joined
Mar 25, 2013
Messages
1,672
Sounds like a windows or driver problem. Or it could be a motherboard issue.

Did you install the Samsung NVME driver and not just keep the windows driver? Is the BIOS of the motherboard updated?
 

SPARTAN VI

Supreme [H]ardness
Joined
Jun 12, 2004
Messages
8,025
Sounds like a windows or driver problem. Or it could be a motherboard issue.

Did you install the Samsung NVME driver and not just keep the windows driver? Is the BIOS of the motherboard updated?

Leaning toward motherboard or the SSD itself since the problem persisted after a format and reinstall of Win10. I installed the Samsung NVMe driver, didn't touch the Windows driver wherever that lies. I did update the BIOS as well; went from version 19?? to 2202.
 

/dev/null

[H]F Junkie
Joined
Mar 31, 2001
Messages
15,190
How are read speeds from a linux live cd?

find the device name & try:

dd if=<device> of=/dev/null bs=1M
 

Slug

Limp Gawd
Joined
Dec 4, 2004
Messages
173
Any chance you are running Eset AV? That has a known issue with Samsung magician. If you are, disable it and re-run the test.
 

thesmokingman

Supreme [H]ardness
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Nov 22, 2008
Messages
6,617
When I first installed my 950 Pro m2, I didn't have to mess with it in bios on my Formula. It was already set to the right settings by default. And even with the standard driver, it was pulling down 1800MB/s reads. The Samsung driver pushed that to over 2200MB/s though so the problem isn't just a driver.

I would install AIDA64 so you can check m2 temps. I would reset the MB bios and just change what you need and not touch the SSD settings then test again while checking temps.
 
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