Samsung EVO 960 500GB massive write performance drop when used as boot drive

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Zaporro

Zaporro

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Jan 23, 2014
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My Samsung EVO 960 500GB experiences massive write speed performance drop when its used as a OS boot drive (windows 10 pro 64 bit 16299).

With EVO being OS/boot drive the write sequential write drops as low as 460MB/s, random write IOPS 20000. I tested both with Samsung Magician and Cristal Disk Mark. Read benchmarks are all good while read ones drop to hell, 4x less or even more.

Im using newest firmware, Samsung driver, PCIE runs in x4 mode gen 3.

The curious thing is that, i have a secondary windows installation on unconnected drive, if i connect that drive and then my EVO960 becomes a secondary non-OS drive, when i run Samsung Magician benchmark or Crystal Disk Mark, even when using Microsoft drivers im getting full performance including ~1800MB/s sequential write and over 200000 random write IOPS.

What is going on?? For the time of test i disconnected internet and disabled antivirus. In HWinfo64 temperature does not exceed 50 celcius. When not doing anything, before or after test i can see my EVO go idle (<1% total host activity).

Code: 
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CrystalDiskMark 6.0.0 x64 (C) 2007-2017 hiyohiyo
                          Crystal Dew World : https://crystalmark.info/
-----------------------------------------------------------------------
* MB/s = 1,000,000 bytes/s [SATA/600 = 600,000,000 bytes/s]
* KB = 1000 bytes, KiB = 1024 bytes

   Sequential Read (Q= 32,T= 1) :  3306.939 MB/s
  Sequential Write (Q= 32,T= 1) :   467.836 MB/s
  Random Read 4KiB (Q=  8,T= 8) :  1037.660 MB/s [ 253335.0 IOPS]
 Random Write 4KiB (Q=  8,T= 8) :    84.866 MB/s [  20719.2 IOPS]
  Random Read 4KiB (Q= 32,T= 1) :   438.223 MB/s [ 106988.0 IOPS]
 Random Write 4KiB (Q= 32,T= 1) :    48.737 MB/s [  11898.7 IOPS]
  Random Read 4KiB (Q=  1,T= 1) :    43.443 MB/s [  10606.2 IOPS]
 Random Write 4KiB (Q=  1,T= 1) :     2.029 MB/s [    495.4 IOPS]

  Test : 1024 MiB [D: 50.1% (150.4/300.0 GiB)] (x3)  [Interval=5 sec]
  Date : 2018/04/04 20:29:32
    OS : Windows 10 Professional [10.0 Build 16299] (x64)
 
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Something called an OS, in this case windows, happened? I am can only guess that the OS is putting a load on the SSD or disk I/O load on the boot drive SSD. I speculate a lot of it is probably file handles, security, and locking and permission stuff.
 
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Hello,

I think i found the culprit of performance drop but i still dont understand why it happens. When I go to disk properties -> hardware -> properties -> change settings -> rules (2nd tab) there are two checkboxes there

the first one is "turn on data write buffering for this device, increases system performance by turning in write buffering on drive but power loss or device failure may cause data loss"

the box is ticked on by default with it on I get max speeds (250k+ write IOPS and 1800MB/s write speed). The very second I untick it all write speeds go to hell, and thats exactly what i did right before my issue started happening (was worried about that data loss). I got someone else to verify their EVO and do benchmark with that box ticked off and when they did it they suffered same performance drop.

So i just ticked it on back now and i got my write performance back. But is this supposed to work that way? How come an Windows function is responsible for EVO performance that is advertised everywhere (not everyone uses Windows). Or does that checkbox control something in the SSD hardware?
 
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