I am working on Magento Optimization steps
What is the meaning of "Use a memory-based filesystem for dynamic data" ?
How to apply it ?
You can mount the public_html/var/cache folder on ramdisk - as root on the server do:
mount -t tmpfs cache/ cache/
from the var folder in Magento to enable this. You will need to make sure that the folder is writable by the web user (by making it 0775 and owned by the group that the web server runs as, or *as a last resort* making it 0777).
I would like to point out that putting `var` on ramdisk is some pretty old advice. I wouldn't do this any more - I'd recommend using Memcache or Redis as your cache, or at the very least running Colin Mollenhour's Cm_Cache_Backend_File
File system is the default what magento use for caching, you need to change it to faster caching solution like memcached, redis cache, varnish ... to speed up magento