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http://www.agildata.com/database-sharding/
What Drives the Need for Database Sharding?
Database Sharding is a highly scalable approach for improving the throughput and overall performance of high-transaction, large database-centric business applications. Since the inception of the relational database, application engineers and architects have required ever-increasing performance and capacity, based on the simple observation that business databases generally grow in size over time. Adding to this general trend is the extreme expansion of business data due to the evolution of the Internet economy, the Information Age, and the prevalence of high-volume electronic commerce.
As any experienced database administrator or application developer knows all too well, it is axiomatic that as the size and transaction volume of the database tier incurs linear growth, response times tend to grow logarithmically. This is shown in the following diagram:
Figure 1. The growth in database transactions and volumes has a large impact on response times.
The reasons for the performance and scalability challenges are inherent to the fundamental design of the database management systems themselves. Databases rely heavily on the primary three components of any computer:
- CPU
- Memory
- Disk
Through benchmark tests that we have performed, we know that each of these elements on a single server can only scale to a given point, and then other measures must be taken. While it is clear that disk I/O is the primary bottleneck, as database management systems have improved they also continue to take greater advantage of CPU and memory. In fact, we have observed that it is the matching of these three factors that determines maximum performance. In other words, you cannot add an unlimited number of CPUs (or processing cores) and see a commensurate increase in performance without also improving the memory capacity and performance of the disk drive subsystem. It is also common to see a diminishing return as resources are added to a single database server. These factors are especially true in mixed-use business transaction systems; systems that perform a high volume of read and write transactions, as well as supporting generalized business reporting tasks.
Therefore, as business applications gain sophistication and continue to grow in demand, architects, developers and database administrators have been presented with a constant challenge of maintaining database performance for mission critical systems. This landscape drives the need for Database Sharding.