entries in error_log

[mistwang]

increase connection timeout to 120. If your server do not have enough bandwidth, you may have network problem. LiteSpeed delivers content much faster than Apache, which may make it looks worse. Better ask you DC about your bandwidth limit, and your usage. on 10Mb/s, 100Mb/s or 1Gb/s port, and QoS limit has been applied, etc.
Check the output of "netstat -s" for retransmission, packet loss, etc.

 

[zep]

May fix your issue

I had the same issue, altho I have a new one now, to fix the 503 on my server I had to add the 'm' to the end of Memory Soft Limit (bytes) and Memory Hard Limit (bytes) (running fedora, dedicated) Hope that helps