EnhanceIO settings

create eio cache:

eio_cli create -d <HDD_slow_drive> -s <SSD_cache_drive> -p fifo -m wb -b 4096 -c comment

EnhanceIO create persistent udev file, which start cache after server reboot. File is located under /etc/udev/rules.d.

eio setting are done in /proc/sys/dev/enhanceio/<cache>. One special, undocumented function/param is cache_wronly. Set cache_wronly to "1" cause write only caching. Read requests will be satisfied without saving them to cache.

Suitable settings for drbd backup:

cache_wronly: 1
dirty_high_threshold: 90
dirty_low_threshold: 70
dirty_set_high_threshold: 95
dirty_set_low_threshold: 30
mem_limit_pct: 75
time_based_clean_interval: 20