My debian 8 machine has 2 drives. Sometimes I move/copy files from drive A to drive B. Drive B is slow, so the file system cache is full causing the system to be slow/unresponsive when copying large files. To avoid that i wanted to limit the file system cache to be used for device B. Therefore i changed the setting /sys/class/bdi/MAJOR:MINOR/max_ratio from 100 to 20. However that doesn't seem to take effect. What am I missing? Do I need to do anything to reload those settings? Is there another way to limit file system cache for a specific device?
I have already tried mount option "sync". That works, but makes drive B terribly slow.
