Oracle’s Exadata is a self-contained database appliance. Traditional database architecture would have a server that contained the CPU, memory and enough hard drive space to house the Operating System connected through a network to an array of hard drives for all other storage. Scalability was achieved through adding additional database servers and creating a cluster, and expanding the back end array. This traditional architecture resulted in poorer performance in read and write intensive applications such as Data Warehousing due to bottlenecks in the storage array.
Database appliances combine the processing with the storage achieving exponentially faster performance by having onboard dedicated storage and software to manage the distribution of data across that storage.
The pros of Exadata are:
• Hardware is easy to deploy
• The system is faster than comparable data models on traditional architecture
• Oracle 11g holds the record for the fastest OLTP. http://www.tpc.org/tpcc/results/tpcc_perf_results.asp
• Scalability is easy – just add additional nodes or Oracle’s storage expansion rack
• Integration with a Oracle product line that has a lot of depth
The cons of Exadata:
• Performance on some queries may dramatically change for the worst and need extensive tuning
• The optimizer is not well understood by anyone (including Oracle support) which leads to the first con
• The storage management software, while has gotten better since the 1st generation of the product, has a tendency to be buggy
• Requires a lot of administration by DBAs.
• 1st generation Exadatas on the HP hardware are crap.
• They are expensive – both licensing and hardware and not all of the database software is included in the Exadata price. Single full rack database machine and storage with full support is around 1.5 million (doesn’t include the year over year licensing). http://www.oracle.com/us/corporate/pricing/exadata-pricelist-070598.pdf
The main thing to point out with this hardware is that it is purpose built. While Oracle might market it as the single database appliance to end all, it is still not a best practice to combined mixed workloads (OLTP/OLAP) into the same physical or logical architecture. Performance to an extent in OLAP is still driven by having an appropriate and performing data model. Hardware will only provide so much of a boost and is still driven by the logical design of the database.
I would recommend Exadata if you are moving from an Oracle legacy system. If you are looking to move from another vendor, then the process is going to be rather difficult in getting it to work on Oracle. If you are building from the ground up, then it depends on the budget you have to work with.
Main competitors of the Exadata – PureSystems by IBM (FNA Netezza), Teradata, EMC’s Greenplum.