Expert Oracle Exadata - Parent Directory

CHAPTER 15 COMPUTE NODE LAYOUTCPU Resources: When determining the optimal node layout for your databases,keep in mind that Exadata handles the I/O workload very differently fromtraditional database platforms. On non-Exadata platforms the database serveris responsible for retrieving all data blocks from storage to satisfy I/O requestsfrom the applications. Exadata offloads a lot of this work to the storage cells.This can significantly reduce the CPU requirements of your database servers.Figuring out how much less CPU your databases will require is a difficult taskbecause it depends, in part, on how much your database is utilizing parallelquery and HCC compression, and how suitable your application SQL is tooffloading. Some of the Smart Scan optimizations, such as decryption,predicate filtering, and HCC decompression, will reduce CPU requirementsregardless of the type of application. We covered these topics in detail inChapters 2–6.Systems requiring thousands of dedicated server connections can overwhelmthe resources of a single machine. Spreading these connections across multiplecompute nodes reduces the burden on the system’s process scheduler andallows the CPU to spend its time more effectively servicing client requests. Loadbalancing connections across multiple compute nodes also improves thedatabase’s capacity for handling concurrent connection requests.Memory Resources: Systems that require thousands of dedicated serverconnections can also put a burden on memory resources. Each dedicatedserver connection requires a slice of memory, whether or not the connection isactively being used. Spreading these connections across multiple RAC nodesallows the database to handle more concurrent connections than a singlecompute node can manage.I/O Performance and Capacity: Each compute node and storage cell isequipped with one 40Gbps QDR, dual-port InfiniBand card through which, inpracticality, each compute node can transmit/receive a maximum of 3.2gigabytes per second. If this is sufficient bandwidth, then the decision ofmoving to a multi-node RAC configuration may be more of an HAconsideration. If you have I/O-hungry applications that require morethroughput than one compute node can provide, then RAC may be used toprovide high availability as well as additional I/O capacity.Patching and Testing: Another key consideration in designing a stable databaseenvironment is providing a separate area where patches and new features canbe tested before rolling them into production. For non-Exadata platforms,patching and upgrading generally involves O/S patches and Oracle RDBMSpatches. Exadata is a highly complex database platform, consisting of severaladditional hardware and software layers that must be patched periodically,such as Cell Server, CellCLI, ILOM firmware, InfiniBand switch firmware,InfiniBand network card firmware, and OFED drivers. As such, it is absolutelycrucial that a test environment be isolated from critical systems to be used fortesting patches.498