Expert Oracle Exadata - Parent Directory

C H A P T E R 1•••What Is Exadata?No doubt you already have a pretty good idea what Exadata is or you wouldn’t be holding this book inyour hands. In our view, it is a preconfigured combination of hardware and software that provides aplatform for running Oracle Database (version 11g Release 2 as of this writing). Since the ExadataDatabase Machine includes a storage subsystem, new software has been developed to run at the storagelayer. This has allowed the developers to do some things that are just not possible on other platforms. Infact, Exadata really began its life as a storage system. If you talk to people involved in the development ofthe product, you will commonly hear them refer the storage component as Exadata or SAGE (StorageAppliance for Grid Environments), which was the code name for the project.Exadata was originally designed to address the most common bottleneck with very large databases,the inability to move sufficiently large volumes of data from the disk storage system to the databaseserver(s). Oracle has built its business by providing very fast access to data, primarily through the use ofintelligent caching technology. As the sizes of databases began to outstrip the ability to cache dataeffectively using these techniques, Oracle began to look at ways to eliminate the bottleneck between thestorage tier and the database tier. The solution they came up with was a combination of hardware andsoftware. If you think about it, there are two approaches to minimizing this bottleneck. The first is tomake the pipe bigger. While there are many components involved, and it’s a bit of an oversimplification,you can think of InfiniBand as that bigger pipe. The second way to minimize the bottleneck is to reducethe amount of data that needs to be transferred. This they did with Smart Scans. The combination of thetwo has provided a very successful solution to the problem. But make no mistake; reducing the volumeof data flowing between the tiers via Smart Scan is the golden goose. Kevin Says: The authors have provided an accurate list of approaches for alleviating the historical bottleneckbetween storage and CPU for DW/BI workloads—if, that is, the underlying mandate is to change as little in thecore Oracle Database kernel as possible. From a pure computer science perspective, the list of solutions to thegeneric problem of data flow between storage and CPU includes options such as co-locating the data with thedatabase instance—the “shared-nothing” MPP approach. While it is worthwhile to point this out, the authors areright not to spend time discussing the options dismissed by Oracle.In this introductory chapter we’ll review the components that make up Exadata, both hardware andsoftware. We’ll also discuss how the parts fit together (the architecture). We’ll talk about how thedatabase servers talk to the storage servers. This is handled very differently than on other platforms, sowe’ll spend a fair amount of time covering that topic. We’ll also provide some historical context. By the1