On my APU2E4 with 4GB ECC RAM,
I use the spare space on the SSD as a mount point for the scanner and other small file stuff, which is really cool (6-10W).
-> NFS server and SMB server.
However, I‘m wondering why my RAM usage tells me on LuCI
Total Available 3.54GB/3.84GB
Used 3.2GB
Buffered 5.2MB
Cached 2.91GB
Is this normal, am I going to have issues or will the RAM (cached?) going to be flushed after some time ?
I don't see that this is huge problem on your side.
Cached is specially region of memory that holds read caching from disk devices.
Like you read sectors 1, 2, 3. Then nothing happens for 5 mins and you need to read same sectors again. If there wasn't cache they will be read from device again. But since they are in disk cache memory region - they're just return from it without actually make read operation from device.
This region won't be flushed. But if some memory hungry app was started then system will start releasing memory from "cached" to app.
Here is documentation from help:
buffers
Memory used by kernel buffers (Buffers in /proc/meminfo)
cache Memory used by the page cache and slabs (Cached and SReclaimable in /proc/meminfo)
buff/cache
Sum of buffers and cache
Linux configuration occupy 100% of free memory to be used from cache.