Replication and server down, PHP. Can not get/store data

Hi,

I have a 2 node 1.8.0 couchbasesystem.
CentOS 6.2
The bucket is "default" as a couchbase type that is replicated to 1 copy.
Using PHP to connect to cluster. From following SDK:
http://packages.couchbase.com/clients/php/php-ext-couchbase-1.0.4-centos...

My theory is to replace memcached for a better solution with replication and to remove a SPOF. If this is possible with couchbase.

I'm connection to server 1.
When both servers are up and running its 100% working with both read and write.

If I turn server 2 off(shutdown service on centos) the result is different. Only 50% of the read/write will work.
I do not make a failover or rebalance.(the failover should occur anyway after 30 sec but it might need 3 servers to do that?).

First Question is, do I need 3+ servers to have a 100% working replication? I need 100% uptime of the data. My thought is that since I have two servers the first server would use the replica items when server two is turned off.

Some code I try to test with:

Case 1:
If server two is off. Following code will not work.

$cb = new Couchbase("192.168.0.1:8091");
$i=94;
$cb->set("a_$i", $i);
var_dump($cb->get("a_$i"));

It will result in:
PHP Warning: Couchbase::set(): Failed to store a value to server: Connection failure

If server two is up, it will work as intended(192.168.0.1 is ip for server 1). If I change $i to for example 83 it will work since it wants to position it on server 1.

Case 2:
If I do a loop.

$cb = new Couchbase("192.168.0.1:8091");
for($i=1;$i<=100;$i++) {
echo "---------$i--------\n";
$cb->set("a_$i", $i);
var_dump($cb->get("a_$i"));
echo "-----------------\n";
}

This will result in having approx 50% of the keys written/read correct. Why does it even try to write on server two, since the couchbasecluster knows its down. It seems it reports all servers of the cluster no matter what state they are in.

Have I missunderstood it all or am I doing something wrong?
All help is appreciated!