Why is my sequential read speed so (comparatively) slow?
While CrystalDiskMark on Win10 reports around 5GB/s (for reading as well as writing), I just do not get close to that performance on Linux. (A copy&paste of several hundreds of GBs on Windows from/to the same drive averaged around 2,5GB/s, so I do not think CDM is far off from real values here.)
dd if=/dev/nvme0n1 of=/dev/null bs=1M count=10k
reports a mere 1.5GB/s.
On another NVME (both being Corsair Force MP600 1TB) dd reports 1.4 GB/s.
I would expect that such a sequential access is the best-case for reading from any storage device, so I really have no clue on what is going on here.
(I saw some similar questions on StackExchange, but they all went into different directions than this 'simple one'.)
Note aside: CrystalDiskMark uses 'real files' if I'm not mistaken - so it has even additional file system overhead, whereas my dd call should be the best one could possibly get - or not?
- both NVMEs are connected with 4 PCIe 4.0 lanes
- temperature of both NVMEs < 60°C
- the faster one is also mounted as root, the slower one was unmounted
- Zen2 Threadripper (so more than enough PCIe 4.0 lanes..)
- Kernel 5.6.4
- BIOS up2date
- NVME firmware up2date
Any ideas or pointers into the right direction would be greatly appreciated!