Basic Memcache Questions in PHP

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I have never used memcache before now so please excuse my inexperience. Although it is pretty self explanatory, I would like to make sure I am using the built in functions correctly as I am creating a class that will be used commercially so it must be correctly coded and efficient.I have several questions but as they are very basic I felt it would be alright to combine them into one Stackoverflow question.If they require an essay answer, please dont bother and I will post it up as a separate question[*]When would I need to use \[code\]memcache::addServer\[/code\] and what is the difference between this and \[code\]memcache::connect\[/code\]?[*]Does memcache overwrite stored values if it runs out of memory, even if the item has not yet expired?[*]What would I use \[code\]memcache::getExtendedStats\[/code\] for?[*]How do I check to see if a connection to memcache already exists and if not, create a connection?[*]If I have my usual memcache server of 'localhost' set up, how would I go about setting up another memcache server on my same dedicated server? [*]Apart from more memory, what is the benefit of having more than one memcache server?[*]Should I check for memcache server updates regularly?[*]Does it use a lot of memory to run memcache::connect at the beginning of each page, even if I am not using it?[*]When am I likely to return errors and how do I catch these?[*]Most importantly, if I am using memcache within another class that has several methods that may be called more then once per script, how should I go about initialising the object and connecting to the server within each method?My guess for the last question would be to do it like so:\[code\]class test { public function blah(){ // Make sure the memcache object is accessible global $memcache; // Do something ... // Save result in memcache $memcache->set(...); } public function foo(){ // Do something ... // No use for memcache }}// Initialise each class$test = new test;$memcache = new memcache;$memcache->connect(...);// Call some methods from the test class$test->blah();$test->foo();$test->blah();\[/code\]As you can see in the above example, I connect to the memcache server at the beginning of the script. If I was to include this at the beginning of every page, even on pages that do not use memcache, would this increase the response time a lot or minimal amounts? Hence, question 8!