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PCIe 4.0 SSDs, CPU Cores And Random Read/Write Performance

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PCIe 4.0 SSDs, CPU Cores And Random Read/Write Performance

Postby Ian on Thu Feb 25, 2021 4:18 pm

Something I've been thinking a lot about lately (yeah, I lead a boring life :wink: ) is how the number of CPU cores and threads impacts the random read/write performance of PCIe 4.0 SSDs. With SATA and PCIe 3.0 SSDs, you could easily max out a drive's random read/write performance using a CPU with 4 cores (or 8 threads). With many of the newer PCIe 4.0 SSDs, that's not really the case.

For example, when I reviewed the Samsung 980 PRO last fall, I was not able to reach the magic 1 million IOPS number. According to Samsung, you needed at least 16 threads and my AMD Ryzen 3 3100, with its 4 cores (8 threads), was not up to the task. With this CPU, I couldn't even generate half a million IOPS.

I recently upgraded the CPU in my test system to an AMD Ryzen 7 3700x. The main reason for this was that it had twice the number of cores (8) as the 3100 and I could use 16 threads in my benchmarks. I ran some quick benchmarks and was surprised by the results.

Samsung 980 Pro 2TB Iometer 3700x.png
Samsung 980 Pro 2TB Iometer 3700x.png (40.85 KiB) Viewed 807 times


First and foremost, I still wasn't able to hit that magic 1 million IOPS number. With twice the cores, I was able to squeeze another 300k IOPS out of the drive when doing random reads, but it still came up short. Maybe I need more cores or AMD's x570 chipset?

The other thing I noticed was that even with the same number of threads, the 980 PRO performed much better with the 3700x. The base clock speed on the two processors is the same and, aside from the number of cores, the biggest difference is the size of the L1 (256KB vs 512KB), L2 (2MB vs 4MB) and L3 (16MB vs 32MB) caches. Is this enough to give the drive's random read/write performance a boost?

Long story short, if you're buying a PCIe 4.0 SSD like the Samsung 980 PRO and you want to get the most out of its random read and write performance, don't cheap out on your CPU. Instead, buy one that has 8 or more cores. Otherwise, stick with a PCIe 3.0 SSD or one of the entry level PCIe 4.0 SSDs like the ADATA XPG GAMMIX S50 Lite.
"Blu-ray is just a bag of hurt." - Steve Jobs
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Ian
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Re: PCIe 4.0 SSDs, CPU Cores And Random Read/Write Performan

Postby Ian on Thu Feb 25, 2021 9:40 pm

Ran a few more tests before I had to pull out the 980 PRO and start testing another drive. Here are similar results with CrystalDiskMark. Both were with 8 threads. Take note the drive's random read and write performance was better with the 3700x.

Samsung 980 Pro 2TB CDM Comparison.png
Samsung 980 Pro 2TB CDM Comparison.png (182.25 KiB) Viewed 801 times


And again with 16 threads. Still not a million IOPS.

Samsung 980 Pro 2TB CDM Peak T16.png
Samsung 980 Pro 2TB CDM Peak T16.png (37.93 KiB) Viewed 801 times
"Blu-ray is just a bag of hurt." - Steve Jobs
User avatar
Ian
Grand Poobah
 
Posts: 15077
Joined: Sun Apr 08, 2001 2:34 pm
Location: Madison, WI


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