Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File Size

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Mako88
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Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File Size

Postby Mako88 » Tue Apr 28, 2015 5:31 pm

Hmmm, comparing my newly installed SM951 to scores that are posted on various review sites, and it's performing extremely well in the larger file read/writes, nearly identical to others results, but is getting killed in 4k tests...particularly high que depth 4k tests.

It's about -45% lower than the marks should be in the following specific test spots:

Anvil 4K QD16 : Scores 98,473 IOPS, should be around 150,000 IOPS

ATTO - Everything Below 64.0 K: Scores are off on 0.5 through 64.0 by -30 to -50%, then magically catch back up to 100% where they should be by 256.0...odd)

CrystalDiskMark 4K Q32T1: Scores 337.2/308.8 while it should be around 512/450

AS SSD 4K-64Thrd: Scores 400/361 while it should be around 680/360

ASS SSD Copy-Benchmark, "Program": Scores 417 MB/s with a 3.37 s duration, should be around 780 MB/s with a 1.80 second duration

HD Tune Pro 5.50 4K random multi (32): 47202 IOPS, should be around 100000 IOPS

I'm running Windows 7 on an MSI X99S Gaming 7 (4x lanes)...any particular OS setting or something that should be checked that would affect the smaller file transfers?

It's strange because what I've listed above are the only areas within each benchmark that were off, the other 20+ measurements within those tests were spot on. Wonder what I'm missing.

My full benchmark results: http://i.imgur.com/iKny0sj.jpg

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Re: Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File

Postby Apoptosis » Wed Apr 29, 2015 7:46 am

I am also noticing lower than expected 4KB performance at a QD of 32... The SM951 results are not anything close to what I expected and I don't have any good answers for you.

I've been working with Samsung trying to get answers, but I've been waiting on answers to what I would think are fairly simple questions for more than a week. It appears that these OEM drives are not a priority to them even though they are getting a cult following among enthusiasts.

The SM951 AHCI 512GB drive is tested after a Secure Erase and the SM951 NVMe 256GB drive has not been secure erased as there is no easy utility out there that can do it and my Linux kung fu is weak although I know there is a way to do it under Linux.

When I made these charts just for you I messed up the bottom axis. It should be 100% to 0% not 100% to 1100%

4k-random-odd.jpg
4k-random-odd.jpg (66.58 KiB) Viewed 4085 times

4k-random-odd2.jpg
4k-random-odd2.jpg (69.7 KiB) Viewed 4085 times
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Mako88
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Re: Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File

Postby Mako88 » Wed Apr 29, 2015 12:28 pm

Apoptosis wrote:I am also noticing lower than expected 4KB performance at a QD of 32... The SM951 results are not anything close to what I expected and I don't have any good answers for you.

I've been working with Samsung trying to get answers, but I've been waiting on answers to what I would think are fairly simple questions for more than a week. It appears that these OEM drives are not a priority to them even though they are getting a cult following among enthusiasts.

The SM951 AHCI 512GB drive is tested after a Secure Erase and the SM951 NVMe 256GB drive has not been secure erased as there is no easy utility out there that can do it and my Linux kung fu is weak although I know there is a way to do it under Linux.

When I made these charts just for you I messed up the bottom axis. It should be 100% to 0% not 100% to 1100%


Thanks Apoptosis, I saw your other thread and was hoping you'd found out the issue, Anandtech also had issues with their SM951 NVME drive, must be some bugs left.

I have my issue narrowed down to what (I think) are the likely culprits:

1. Intel's IRST driver not being used/or wrong version installed.

That's a tough one because IRST is a pain in the ass, it gives me "this platform is not supported" garbage when I go to install it, etc, and I'm not sure how to get around it.

2. My OS drive is an old Windows 7 install on an Intel 510 SSD, and that install was done via IDE mode within that board's bios long ago...which means that I had to flip my bios sata settings to IDE for that port to get the OS to boot properly after upgrading to the new motherboard/system. I'm wondering now if that's creating an issue on the other sata ports, even though they are set to UEFI properly.

I retested my SM951 last night and it's gotten worse, now on say ATTO it's producing 25000-50000 on each of the tests at 64KB file size and below, and then suddenly jumps at 128KB all the way up to 1500000 read/write once it hits 128KB file size. What a mess, looking forward to Windows 10, will do a clean install at that point and hopefully fix whatever issue there is here.

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Re: Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File

Postby Apoptosis » Wed Apr 29, 2015 4:00 pm

Yeah, I'm having many issues with the Microsoft Driver for NVMe that comes in Windows 8.1. The Microsoft NVMe driver in Windows 8.1 is creating FUA (Force Unit Access) I/O write commands that is causing low scores in PCMark 8 and some of the other applications. Intel NVMe drivers do not need the FUA command, so it isn't used at all. Samsung has advised me to disable FUA, but won't tell me how to do so. I spoke with half a dozen of the developers over at Futuremark and they told me not to disable FUA, but then said they don't have any NVMe drives to try out to help trouble shoot the issue. I've reached out to a number of people and only a handful of people really handful of people are in the inner circle as to what is going on here.

NVMe is still pretty cutting edge and it will be a bit to get some of the kinks worked out. Right now I have questions pending with Samsung that I've been waiting to get answered for weeks. I think I might go ahead and post what I have as other sites are already publishing reviews before there are resolutions to the issues. I guess I'll join the bandwagon and add the information that I have collected while trying to figure out what is going on.

I don't plan on going back and testing these new drives on Windows 7 as Windows 8.1 is solid and Windows 10 is right around the corner. For NVMe drives Windows 8.1 or Windows 10 is a must in my book. I'll be moving to Windows 10 pretty quickly due to this.
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Re: Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File

Postby redstorm » Thu Apr 30, 2015 2:47 pm

The reason the microsoft driver is issuing FUA IO commands to the SM951 is quite simple. The SM951 does not have a battery backed cache, so it cannot guarantee writes in a power loss situation.

This is not the case with the Intel 750 as they have full power loss protection and hence FUA IO commands are not required.

If you can disable FUA and you have a power loss situation when it is writing you will lose or corrupt data most likely.

See here for the spec, explains why it is happening.

https://msdn.microsoft.com/en-us/library/windows/hardware/jj134356.aspx
Search the page for "FUA" to find the relevant section.

Code: Select all

WRITE(10). Support for force unit access (FUA) is mandatory for individual physical disk drives or RAID controllers that contain volatile (non-battery-backed) cache memory and must cause the data sent with this command to be committed to physical media before the command completes.

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Re: Samsung SM951 AHCI SSD Performing Poorly At Sub-4k File

Postby larryccf » Fri May 01, 2015 1:31 pm

Mako88 wrote:.......

I have my issue narrowed down to what (I think) are the likely culprits:

1. Intel's IRST driver not being used/or wrong version installed.

That's a tough one because IRST is a pain in the ass, it gives me "this platform is not supported" garbage when I go to install it, etc, and I'm not sure how to get around it.

2. My OS drive is an old Windows 7 install on an Intel 510 SSD, and that install was done via IDE mode within that board's bios long ago...which means that I had to flip my bios sata settings to IDE for that port to get the OS to boot properly after upgrading to the new motherboard/system. I'm wondering now if that's creating an issue on the other sata ports, even though they are set to UEFI properly.

I retested my SM951 last night and it's gotten worse, now on say ATTO it's producing 25000-50000 on each of the tests at 64KB file size and below, and then suddenly jumps at 128KB all the way up to 1500000 read/write once it hits 128KB file size. What a mess, looking forward to Windows 10, will do a clean install at that point and hopefully fix whatever issue there is here.



FWIW - i had the same issue installing IRST (latest vs i saw was Version: 13.6.0.1002) with my xp941, but found a note on intel's download page that ".....The driver should be installed after the operating system has been installed. F6 and RAID BIOS configurations need to be performed prior to installation of this driver for proper operation." As i wasn't entirely confident it had installed correctly or fully after i installed win 7 64x, i re-installed it per the intel indication, using intel's " SetupRST.exe"

https://downloadcenter.intel.com/downlo ... AID-Driver

BTW, did any of the SSD Optimization tips from The SSD Review help?


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