Comment by kristopolous

For write loads this is expected, even for good drives, at some level. They tend to have some faster storage which takes your writes and the controller later pushes the changes to the main body of the drive. If you write in bulk the main, slower, portion can't keep up so the faster cache fills and your write has to wait and will perform as per the slowest part of the drive. Furthermore: good drives tend to have an amount of even faster DRAM cache too, so you'll see two drop-offs in performance during bulk write operations. For mainly read based loads any proper SSD¹ will outperform a traditional drive, but if your use case involves a lot of writing³ you need to make more careful choices⁵ to get good performance.

I can't say I've ever seen a recent SSD (that isn't otherwise faulty) get slow enough to say it is outperformed by a traditional drive, even just counting the fastest end of the disk, but I've certainly seen them drop to around the same speed during a bulk write.

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[1] unlike this sort of thing: https://www.tomshardware.com/news/low-performance-external-m...

[2] get SLC-only⁴ drives, not QLC-with-SLC-cache or just-QLC, and so forth

[3] bulk data processing tasks such as video editing are where you'll feel this significantly, unless your number-crunching is also bottlenecked at the CPU/GPU

[4] SLC-only is going to be very expensive for large drives, even high-grade enterprise drives tend to be MLC-with SLC-cache. SLC>MLC>TLC>QLC…

[5] this can be quite difficult in the “consumer” market because you'll sometimes find a later revision of the same drive having a completely different memory and/or controller arrangement despite the headline model name/number not changing at all – this is one reason why early reviews can be very misleading

I think cheaper QLC chips use a part of their storage space as SLC, which is fast to write. But once you’ve written the fast part that fits in the SLC cache write throughput quickly tanks as it has to push the data further in to the slower QLC parts.

I used to use an HP EX920 for my system drive and it was abysmally slow at syncs. I'd open Signal and the computer would grind to a halt while it loaded messages from group chats. After much debugging, I found out Signal was saving each message to sqlite in a transaction causing lots of syncing.

I found some bash script that looped and wrote small blocks synchronously and the HP EX920 was like 20 syncs/sec and my WD RE4 spinner was around 150. Other SSDs were much faster (it was a few years ago so can't remember the exact numbers)

1) Nobody says otherwise about cheap anything NVMe. They're pretty terrible once they've exhausted the write cache. This is well-known and addressed in every decent review by reputable sites.

2) Sustaining throughput seems the least of our problems when some unknown number of NVMe SSDs might be literally losing flushed data.

>Under long term heavy duty, I've routinely seen cheap modern platter outperform cheap brand name NVME.

Saw this happen with previous job. I upgraded several Windows devices too Windows 10 and the fastest PC was a Dell desktop with a HDD.

Midrange to lower-mid laptop coupled with low-end SSD's.