The server has 4 cores and 8 GB RAM, about 10 Joomla sites, different versions, 3-4 of them with lscache plugins. PowerDNS, Postfix, FTP, CSF and modsecurity are enabled.
After sometime OLS is not accessible at 7080 port. I can access CP on 8090 and restart it, so it is functional again.
What can be the reason? Where should I look?