When the filesystem fills and the txlog cannot be written, then the postmaster dies.
postgres@s0188000zeu:/usr/postgres> time echo "copy journaleintrag from '/tmp/j.unl' delimiters '|';" | psql cusejoua
FATAL 2: copy: line 64902, write(logfile 0 seg 2 off 6094848) failed: No space left on device
pqReadData() -- backend closed the channel unexpectedly. This probably means the backend terminated abnormally
before or while processing the request.
connection to server was lost
I think it shoud stay up and running, but deny any modification until the filesystem is extended.
Andreas