Can motherboard be bottleneck for ssd speed on sata?

Question

I have a computer:

• ASRock A320M-DVS R4.0 motherboard
• AMD Ryzen 5 3600 CPU
• AMD Radeon R9 Gamer Series 16 GB RAM
• 2 x Samsung 870 QVO 1 TB SSD

I'm testing SSD write speed on newly installed Ubuntu Desktop 20.04 with no other processes running

dd if=/dev/zero of=/moint-point/tmp bs=4M count=10000 status=progress

I disabled write caching by sync mount option and reniced and ioniced dd process for maximum performance.

After 100 seconds writing speed is only 90MB/s, but disk is capable of 530MB/s

How can I significantly increase writing speed? Do I need to replace motherboard? How to choose it? If I buy SATA - USB 3.0 converter and plug into usb, will it increase?

Answer 1

After 100 seconds writing speed is only 90MB/s, but disk is capable of 530MB/s

It's a "QVO" SSD. Its main flash storage isn't capable of 530MB/s.

The SSD only has a small amount of very fast SLC storage, which it uses as a "write cache" to accept incoming data at maximum speed. After writing is done, the SSD will automatically move data from its cache to the main storage memory.

But if you write data quickly enough to fill the cache, then your writes begin going directly to the main storage space – and your SSD's storage is QLC, so 90 MB/s is about as good as it gets.

• AnandTech: The Samsung 870 QVO SSD Review says that your 1TB QVO has ~40 GB of cache space, and confirms the 80 MB/s QLC write speed.

• Explaining Computers: QLC vs TLC SSDs gives a comparison of Samsung's QVO against EVO (which uses much faster TLC flash for its main storage, but also has more cache as well).

(Note: This is the SSD's internal write cache. It has nothing to do with the operating system's RAM-based write cache, and dd has no control over it.)

How can I significantly increase writing speed?

Get an SSD that doesn't use QLC flash.

Also, probably take a look at NVMe SSDs instead of SATA. The "530MB/s" limit does come from SATA being the bottleneck – SSDs can actually reach several GB/s when not constrained by the SATA connection.

If I buy SATA - USB 3.0 converter and plug into usb, will it increase?

Definitely not. It'll only add more bottlenecks.