[xing]

We have found that older Linux distros, the max allowed size of SHM segments are limited and will cause 503 errors. Best way to test is to leave the apc.shm_size line alone or set it to a value of "4" (4MB) and increase it as you go and as the need arises.

Our wiki has been updated to reflect this problem on some systems.

http://www.litespeedtech.com/community/wiki/