1 Replies - 315 Views - Last Post: 04 February 2019 - 10:31 PM

#1 andrecasal   User is offline

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SSDs in Raid 0 are now faster than RAM 🎉 (finally)

Posted 04 February 2019 - 10:22 PM

Hey guys, I just wanted to share with you a computer configuration I'm particularly excited about. Technology is always evolving and it's fun to think about what kinds of solutions are now doable due to this kind of performance.

Before we dive into this configuration, I just need to explain a few definitions, otherwise this gets confusing.

A form factor defines the physical form of a connector. For example, M.2 and SATA Connectors are two different form factors.
A bus defines how the electrical communication is made between devices. For example SATA and PCIe are two different buses or "bus standards".
A controller interface defines how communication is made between the physical controller and a device driver. For example, NVMe and AHCI are two different controller interfaces, requiring two different device drivers.

So, in order to get the full performance out of an SSD like the Samsung 970 Pro, that has a read speed of 3500 MB/s and a write speed of 2700 MB/s, the SATA 3 bus wouldn't cut it, because it only supports a maximum transfer speed of 6Gbps, i.e. 768 MB/s. So how can we take advantage of this awesome SSD? We need to use a bus that achieves such high speeds, like using 4 lanes of the PCIe Gen3 bus. Each lane is capable of 985 MB/s, so 4 lanes are capable of 3940 MB/s, which is enough for this drive.

But we can go further by using Asus Hyper cards to connect 4x Samsung 970 Pros to 16 PCIe lanes on Raid 0. If we do that, we get a (theoretical) read speed of 14 GB/s and a write speed of 10,8 GB/s.

Take into account that DDR4-3200 (the fastest DDR4 RAM) has a peak transfer rate of 25,6 GB/s. We're not that far off.

But a CPU like the AMD Ryzen Threadripper 2990WX has 64 lanes! Using an ASUS X399 Zenith Extreme we have access to 4 PCIe slots of 16 lanes each. So if we use 4 Asus Hyper Cards for a total of 16 Samsung 970 Pros in Raid 0, we could (theoretically) reach read speeds of 56 GB/s and write speeds of 43,2 GB/s.

But in practice, most normal consumers would want a good graphics card so we'd only have access to 3x PCIe slots, because one would be used for the graphics card, leaving us with 3x Asus Hyper cards and 12x Samsung 970 Pros in Raid 0, for read speeds of 42 GB/s and write speeds of 32,4 GB/s.

In a configuration like this, even though RAM has lower latency, with such a large difference in throughput, RAM becomes the bottleneck. It would be interesting to see the performance enhancement an Operating System could achieve by completely skipping RAM.

Check out this video for a demo of the transfer speeds :)/>

This video explains the difference between the NVMe and the AHCI buses and a few other things.

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Replies To: SSDs in Raid 0 are now faster than RAM 🎉 (finally)

#2 modi123_1   User is online

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Re: SSDs in Raid 0 are now faster than RAM 🎉 (finally)

Posted 04 February 2019 - 10:31 PM

Not particularly industry news... more like a blog post. You can totally utilize that option at the top.

Though it looks like a duplicate of a post you have here already so I'll close this.
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