This is a problem right there. Assuming ext4 filesystem, minimum size of metadata is 256 bytes per file (index node structure). If you have 5M files (not unusual on an average sized node) this combines to 1.2GB, that definitely won’t fit in ram, simply because your also need space for OS and software.
This means most accesses to metadata on your appliance involve roundtrip to disk and are ridiculously slow.
As a side effect, your node is earning less because someone else, who has metadata cached, can start sending data to customers sooner, while your node still scrambles to find the file.