Does an NVME SSD slow down when using it in lvm cache?

Question

Solid State Drives

There is a task, resetting "cold" files from ssd to hdd, you can implement it by creating lvm from hdd and connecting a cache in the form of ssd to it, it turns out that all hot data will spin on ssd, but the question is whether ssd performance will degrade in this scheme because of such an interlayer, rather than the data was purely on ssd?

Answer 1

Depending on what you mean by speed.
The speed of reading / writing directly from the disk will not change in any way - it does not matter to the disk.
But the system will receive information with a delay - latency will increase.
Well, the load on the processor will increase.
Well, when you put a disk in the cache, you need to understand that TRIM will not work, so you need to leave a fairly large over.

Answer 2

As far as I know, LVM understands the difference between SSD and HDD, including all sorts of chips like trim, so bet it shouldn't degrade.

Answer 3

My bcache works well for this purpose.
It all depends on the specific situation - it's easier to collect and conduct a benchmark than to play a guessing game.