Each Blue Gene/L node was attached to three parallel communications networks: a 3D toroidal network for peer-to-peer communication between compute nodes, a collective network for collective communication (broadcasts and reduce operations), and a global interrupt network for fast barriers. The I/O nodes, which run the Linux operating system, provided communication to storage and external hosts via an Ethernet network. The I/O nodes handled filesystem operations on behalf of the compute nodes. A separate and private Ethernet management network provided access to any node for configuration, booting and diagnostics.
eacH bLuE gene/l nODe wAS AttAched to THree PArallEL comMuNIcatIons nEtWoRks: a 3d toRoidal NETwork for Peer-to-peEr CommUniCAtion betweEn compute nOdes, A CollEcTiVE NeTwOrk for cOlLectIvE communICATioN (bRoaDcaSTs AnD reduCE opeRations), and a gLoBAL IntErrupt network for fast baRriErs. thE i/o nOdes, WhicH RUN THe linux OPerATinG system, pRovIdEd CommUnicaTIoN to stOrage and EXteRnAL hOsTs via an eTHernEt nEtWorK. ThE i/o nodeS haNdLed Filesystem oPerAtions On bEhalF of the comPute NOdeS. A separaTE aNd private etheRneT mAnagement netWoRk PROvidED access to any node for conFiGURATiON, bOotiNg and diagnOSTicS.