tailieunhanh - Microsoft SQL Server 2008 R2 Unleashed- P60

Microsoft SQL Server 2008 R2 Unleashed- P60:SQL Server 2005 provided a number of significant new features and enhancements over what was available in SQL Server 2000. This is not too surprising considering there was a five-year gap between these major SQL Server 2008 is not as much of a quantum leap forward from SQL Server 2005 | 534 CHAPTER 18 SQL Server High Availability Now you can extend this fault-tolerant solution to embrace more SQL Server instances and all of SQL Server s related services. This is a big deal because things like Analysis Services previously had to be handled with separate techniques to achieve near high availability. Not anymore each SQL Server service is now cluster aware. Data Replication The next technology option that can be utilized to achieve high availability is data replication. Originally data replication was created to offload processing from a very busy server such as an OLTP application that must also support a big reporting workload or to geographically distribute data for different very distinct user bases such as worldwide product ordering applications . As data replication transactional replication became more stable and reliable it started to be used to create warm almost hot standby SQL Servers that could also be used to fulfill basic reporting needs. If the primary server ever failed the reporting users would still be able to work hence a higher degree of availability achieved for them and the replicated reporting database could be used as a substitute for the primary server if needed hence a warm-standby SQL Server . When doing transactional replication in the instantaneous replication mode all data changes were replicated to the replicate servers extremely quickly. With SQL Server 2000 updating subscribers allowed for even greater distribution of the workload and overall increased the availability of the primary data and distributed the update load across the replication topology. There are plenty of issues and complications involved in using the updating subscribers approach for example conflict handlers queues . With SQL Server 2005 Microsoft introduced peer-to-peer replication which is not a publisher subscription model but a publisher-to-publisher model hence peer-to-peer . It is a lot easier to configure and manage than other replication .