- PostgreSQL Replication Types

I inherited a 9.1 replication environment

Few basic questions that I can't find clear answers / clarifications for if
possible:

3 types of replication in 9.1 I've read about from the offical docs:

1) warm standby
2) hot standby
3) streaming replication

I'm using streaming replication I believe, the only indication I have is
that there is the primary_conninfo on the standby. Is this the only
indication?

Is it possible to get if using streaming replication under normal
operations?

*cp: cannot stat `/opt/postgres/9.1/archive/000000070000000F00000057': No
such file or directory*

*cp: cannot stat `/opt/postgres/9.1/archive/000000070000000F00000057': No
such file or directory*

*LOG: streaming replication successfully connected to primary*

*FATAL: could not receive data from WAL stream: FATAL: requested WAL
segment 000000070000000F00000057 has already been removed*

My understanding is that warm standby and hot standby do log shipping and
there is a greater window for transactions not to be send to the standby
because WAL XLOG must be filled.

Whereas Streaming replication basically sends at the transaction level?

I'm sure this is somewhat misinformed!

Thanks,

Will