We have already finde a rather bland description of how it spec view Oracle Exadata. However, like the well-known tale of the blind men describing an elephant, there are many conflicting perceptions about the nature of Exadata. We will cover a few of the common descriptions in this blog note.
Data Warehouse Appliance
Occasionally, Exadata is described as a data warehouse appliance (DW Appliance). While Oracle has attempted to keep Exadata from being pigeonholed into this category, the description is closer to the truth than you might initially think. It is, in fact, a tightly integrated stack of hardware and software that Oracle expects you to run without a lot of changes. This is directly in line with the common understanding of a DW Appliance. However, the very nature of the Oracle database means that it is extremely configurable. This flies in the face of the typical DW Appliance, which typically does not have a lot of knobs to turn. However, there are several common characteristics that are shared between DW Appliances and Exadata:
- Exceptional Performance: The most recognizable characteristic of Exadata and DW Appliances in general is that they are optimized for data warehouse type queries.
- Fast Deployment: DW Appliances and Exadata Database Machines can both be deployed very rapidly. Since Exadata comes preconfigured, it can generally be up and running within a week from the time you take delivery. This is in stark contrast to the normal Oracle clustered database deployment scenario, which generally takes several weeks.
- Scalability: Both platforms have scalable architectures. With Exadata, upgrading is done in discrete steps. Upgrading from a half-rack configuration to a full rack increases the total disk throughput in lock step with the computing power available on the database servers.
- Reduction in TCO: This one may seem a bit strange, since many people think the biggest drawback to Exadata is the high price tag. But the fact is that both DW Appliances and Exadata reduce the overall cost of ownership in many applications. Oddly enough, in Exadata’s case, this is partially thanks to a reduction in the number of Oracle database licenses necessary to support a given workload. We have seen several situations where multiple hardware platforms were evaluated for running a company’s Oracle application and have ended up costing less to implement and maintain on Exadata than on the other options evaluated.
- High Availability: Most DW Appliances provide an architecture that supports at least some degree of high availability (HA). Since Exadata runs standard Oracle 12c or 11g software, all the HA capabilities that Oracle has developed are available out of the box. The hardware is also designed to prevent any single point of failure.
- Preconfiguration: When Exadata is delivered to your data center, an Oracle engineer will be scheduled to assist with the initial configuration. This will include ensuring that the entire rack is cabled and functioning as expected. But like most DW Appliances, the work has already been done to integrate the components. Hence, extensive research and testing are not required. Having the operating system preinstalled and everything cabled and ready to go in the rack speeds up the time from delivery to implementation immensely.
Regardless of the similarities, Oracle does not consider Exadata to be a DW Appliance, even though there are many shared characteristics. Generally speaking, this is because Exadata provides a fully functional Oracle database platform with all the capabilities that have been built into Oracle over the years, including the ability to run any application that currently runs on an Oracle database and, in particular, to deal with mixed workloads that demand a high degree of concurrency, which DW Appliances are generally not equipped to handle.
This description of OLTP Machine is a bit of a marketing ploy aimed at broadening Exadata’s appeal to a wider market segment. While the description is not totally off base, it is not as accurate as some other monikers that have been assigned to Exadata. It brings to mind the classic quote:
It depends on what the meaning of the word “is” is. —Bill Clinton
In the same vein, OLTP (Online Transaction Processing) is a bit of a loosely defined term. We typically use the term to describe workloads that are very latency-sensitive and characterized by single-block access via indexes. But there is a subset of OLTP systems that are also very write-intensive and demand a very high degree of concurrency to support a large number of users. Exadata was not designed to be the fastest possible solution for these write-intensive workloads, although the latest flash improvements in the X5 models definitely perform better than previous generations. It is worth noting, however, that very few systems fall neatly into these categories. Most systems have a mixture of long-running, throughput-sensitive SQL statements and short-duration, latency-sensitive SQL statements - which leads us to the next view of Exadata.
This description of Consolidation Platform pitches Exadata as a potential platform for consolidating multiple databases. This is desirable from a total cost of ownership (TCO) standpoint, as it has the potential to reduce complexity (and, therefore, costs associated with that complexity), reduce administration costs by decreasing the number of systems that must be maintained, reduce power usage and data center costs through reducing the number of servers, and reduce software and maintenance fees. This is a valid way to view Exadata. Because of the combination of features incorporated in Exadata, it is capable of adequately supporting multiple workload profiles at the same time. Although it is not the perfect OLTP Machine, the Flash Cache feature provides a mechanism for ensuring low latency for OLTP-oriented workloads. The Smart Scan optimizations provide exceptional performance for high-throughput, DW-oriented workloads. Resource Management options built into the platform provide the ability for these somewhat conflicting requirements to be satisfied on the same platform. In fact, one of the biggest upsides to this ability is the possibility of totally eliminating a huge amount of work that is currently performed in many shops to move data from an OLTP system to a DW system so that long-running queries do not negatively affect the latency-sensitive workload. In many shops, simply moving data from one platform to another consumes more resources than any other operation. Exadata’s capabilities in this regard may make this process unnecessary in many cases.