Max Obj Size of 1024 is too small I think. If a page larger than 1K, LSWS will not cache it. Cache Expire time should be shorter, start from 1-5 minutes, just in case that some page should not be cached was cached.
If you use cPanel, you should rebuild Apache with mod_cache support, then go to "service configuration >> Apache Configuration ", Edit Apache include files, edit "Pre Main Include", add
CacheEnable disk /
It will enable cache for all vhosts configured through httpd.conf .
The reason to build Apache with mod_cache and mod_disk_cache is that, Apache will fail configuration test if not.
Yes, using faster disk will help with the performance.
Be conservative with cache configuration, only let web server to cache the page when the page can be cached. be extremely careful with the option that "Ignore Cache control headers".