Don’t worry about that and let the kernel take care of it in form of buffers and cache. I estimate that for a regular ext4 file system for every 1TB of stored node data, metadata take a gigabyte in cache. Meaning, your 48 GB of RAM will be just right when your nodes hit about 48 TB of stored data. If you follow my suggestion to tune down the size of an inode, the number doubles.
And if you trust your UPS, tools like nosync will indeed help.