We have, unfortunately, been experiencing issues with the S1 server over the last week. We believe the issue to be in the LiteSpeed Web Server Software on S1.
We have configured the server to switch to Apache+LSAPI [keeping many of the benefits of LiteSpeed, while using Apache at the core]. This should have been seamless but I personally failed to communicate this to our team effectively resulting in them working to restore LSWS when I switched it to Apache.
Ultimately the miscommunication on my part is the reason for the outage.
We are testing/monitoring the server's performance with Apache 2.4 + MPM Event. One of the primary reasons we switched away from Apache many years ago was due to how resource intensive and bloated Apache was to accomplish the same goals. At the time we were limited to systems with 2 to 8 GB of ram so being conservative of resources was a huge benefit and being faster was great as well.
At this point we're running machines with 100GB of ram or more - often 20 to 50GB of ram just not doing anything at all. As such we don't mind so much the extra resource usage of Apache if it performs better/more reliable than LiteSpeed.
Many of the issues we've faced over the last 6 months have been LiteSpeed related - be it compatible with CentOS7 or simply bugs we've found and had to work to have resolved.
If you have any issues with any of your sites please let us know.