Expert Oracle Exadata - Parent Directory

CHAPTER 1 WHAT IS EXADATA?Single Instance DatabaseRAC DatabaseDatabase ServerDatabase ServerDatabase ServerDatabase InstanceDatabase InstanceDatabase InstanceSingle ASMClusterDBRMASMDBRMASMDBRMASMLIBCELLLIBCELLLIBCELLiDB over InfinibandStorage CellStorage CellStorage CellCELLSRV CELLSRV CELLSRVIORM IORM IORMRS MS RS MS RS MSFigure 1-4. Exadata software architectureAs we’ve discussed, ASM is a key component. Notice that we have drawn it as an object that cutsacross all the communication lines between the two tiers. This is meant to indicate that ASM providesthe mapping between the files and the objects that the database knows about on the storage layer. ASMdoes not actually sit between the storage and the database, though, and it is not a layer in the stack thatthe processes must touch for each “disk access.”Figure 1-4 also shows the relationship between Database Resource Manager (DBRM) running onthe instances on the database servers and I/O Resource Manager (IORM), which is implemented insidecellsrv running on the storage servers.The final major component in Figure 1-4 is LIBCELL, which is a library that is linked with the Oraclekernel. LIBCELL has the code that knows how to request data via iDB. This provides a very nonintrusivemechanism to allow the Oracle kernel to talk to the storage tier via network-based calls instead ofoperating system reads and writes. iDB is implemented on top of the Reliable Datagram Sockets (RDS)protocol provided by the OpenFabrics Enterprise Distribution. This is a low-latency, low-CPU-overheadprotocol that provides interprocess communications. You may also see this protocol referred to in someof the Oracle marketing material as the Zero-loss Zero-copy (ZDP) InfiniBand protocol. Figure 1-5 is abasic schematic showing why the RDS protocol is more efficient than using a traditional TCP basedprotocol like UDP.20