First verify that the VIP used for outgoing traffic has a correct reverse DNS record:
Fix it if necessary. Next, change the
/etc/mailname on every VM. Value should be strictly identical to the reverse.
Last step, indicate to every MTA’s VM to use a custom EHLO value instead of the hostname. For exim simple create a file
/etc/exim4/exim4.conf.localmacros with the following content:
Since version 1.3 Magento can use multiple layer of cache, for example a
memcached for content cache and session, and a database for the rest. This mechanism work pretty well except when you have a connectivity problem.
If Magento is unable to load a session, the request processing will end immediately preventing Apache from logging it. The only information inside the error log will be an
zend_mm_heap corrupted entry.
To ‘fix’ this behavior, you must increase the default timeout for the PHP session handler for a value greater than the TCP re-transmission delay. A 5 seconds value is good enough.