One of our servers Apache was going down frequently and while looking at the Apache error logs we found the following errors.
tail -f /usr/local/apache/logs/error_logs
[Fri May 07 10:42:08 2010] [notice] child pid 30356 exit signal Segmentation fault (11)
[Fri May 07 10:42:09 2010] [notice] SIGHUP received. Attempting to restart
[Fri May 07 10:42:09 2010] [notice] seg fault or similar nasty error detected in the parent process
After investigating a little we manage to find the problem was with PHP failure.
PHP 5.2.9 (cli) (built: Jan 27 2010 15:56:41)
Copyright (c) 1997-2009 The PHP Group
Zend Engine v2.2.0, Copyright (c) 1998-2009 Zend Technologies
with the ionCube PHP Loader v3.3.7, Copyright (c) 2002-2009, by ionCube Ltd., and
with Zend Optimizer v3.3.9, Copyright (c) 1998-2009, by Zend Technologies
Segmentation fault (core dumped)
The core problem was with XCache installed and we have to remove XCache settings on the server from php.ini . Please make sure you are using the correct XCache version which is compatible with Zend Optimizer as XCache do have problems with Zend Optimizer.