Question slow m.2 SSD speeds?

Oct 15, 2019
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I recently replaced my motherboard and CPU. I did not reinstall Windows on my system drive. After replacing, I ran a Samsung Magician benchmark. The two m.2 drives appeared to be considerably slower. So, I ran a CrystalDiskMark on the 3 SSDs in my system. Results below. The results for the 2 m.2 drives seem quite slow (especially the Q=1, T=1 random reads and writes) and the SATA drive seems very fast. Do these look reasonable? Is there something I can check? Thanks in advance for the help.

Asus Prime Z390-A
Intel i9 9900K
32 Gb G.Skill Ripjaw V DDR4-3466 (4x16Gb)

Samsung 960 EVO 500 Gb m.2 (Windows drive)
Sequential Read (Q= 32,T= 1) : 3030.120 MB/s
Sequential Write (Q= 32,T= 1) : 1654.206 MB/s
Random Read 4KiB (Q= 8,T= 8) : 1091.666 MB/s [ 266520.0 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 1180.157 MB/s [ 288124.3 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 285.457 MB/s [ 69691.7 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 239.659 MB/s [ 58510.5 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 41.768 MB/s [ 10197.3 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 133.281 MB/s [ 32539.3 IOPS]

Samsung 970 EVO 500 Gb m.2

Sequential Read (Q= 32,T= 1) : 3545.740 MB/s
Sequential Write (Q= 32,T= 1) : 2491.713 MB/s
Random Read 4KiB (Q= 8,T= 8) : 1030.640 MB/s [ 251621.1 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 715.853 MB/s [ 174768.8 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 310.844 MB/s [ 75889.6 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 268.573 MB/s [ 65569.6 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 46.673 MB/s [ 11394.8 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 150.537 MB/s [ 36752.2 IOPS]

Samsung 850 Pro 256 Gb SATA

Sequential Read (Q= 32,T= 1) : 5445.752 MB/s
Sequential Write (Q= 32,T= 1) : 4586.066 MB/s
Random Read 4KiB (Q= 8,T= 8) : 1724.612 MB/s [ 421047.9 IOPS]
Random Write 4KiB (Q= 8,T= 8) : 1277.459 MB/s [ 311879.6 IOPS]
Random Read 4KiB (Q= 32,T= 1) : 366.854 MB/s [ 89564.0 IOPS]
Random Write 4KiB (Q= 32,T= 1) : 215.677 MB/s [ 52655.5 IOPS]
Random Read 4KiB (Q= 1,T= 1) : 378.961 MB/s [ 92519.8 IOPS]
Random Write 4KiB (Q= 1,T= 1) : 219.274 MB/s [ 53533.7 IOPS]
 
I'm guessing RAM caching (RAPID mode?) is/was turned on for the 850, which makes it's sequential read numbers 100% meaningless....

Numbers for 960 and 970 are quite typical...

I suspect this will end up merely a futile witch hunt. (Help me get back my missing 100 MB/sec speeds on CrystalDiskMark after a mainboard swap and two batches of WIndows updates?) :)

I almost shudder to even ask, but, ....what sort of sequential read/write speeds were you anticipating from the 960 and 970?
 
Last edited:

Darkbreeze

Titan
Moderator
Even with Rapid mode enabled, my 850 EVO doesn't hit anywhere near those numbers, and while the Pro is somewhat faster than the EVO, it isn't THAT much faster. I suspect you are right though, that it is WHY the numbers are so high and personally I'd turn off Rapid mode unless you are making significant large tranfers from that drive to the other drives, often.

The other numbers for the other two drives are in the ballpark, although the 4k QD32 write numbers are not even reasonably close to the specified speeds of more like 450,000 and 330,000 IOPS respectively. Could be many things affecting that though.
 

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