• Each segment instance has PostgreSQL segment listener process
(called Postgres). The port numbers are assigned for this process
during the segment initialization.
• Interconnect : As a portion of work is completed, tuples flow up the query
plan from one gang of processes to the next. This interprocess communica-
tion between the segments are transmitted through the interconnect. It is a
standard Ethernet fabric using UDP protocol by default. UDP provides better
performance and scalability. Alternately, TCP can be used by changing the
gp_interconnect_type from GUC to TCP .
Pivotal added additional packet verification and checking which is not
performed by UDP so the reliability is equivalent to TCP.
• Interconnect is the connection layer between individual database in-
• It is responsible for moving data between the segments during query
• Usually configured as a private LAN; segment servers are not meant
to be visible outside the Greenplum array.
• Consists of Gigabit Ethernet network/fiber switch. (In DCA, the inter-
connect is a 10Gig Ethernet switch. This is a standard recommenda-
tion though there is support for other capacities switch.)
• Has gNet software installed.