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-failover">
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Failover, Replication, Load Balancing, and Clustering Options
+high-availability">
+
High Availability and Load Balancing
Database servers can work together to allow a second server to
- quickly take over if the primary server fails (failover), or to
- allow several computers to serve the same data (load balancing).
- Ideally, database servers could work together seamlessly. Web
- servers serving static web pages can be combined quite easily by
- merely load-balancing web requests to multiple machines. In
- fact, read-only database servers can be combined relatively easily
- too. Unfortunately, most database servers have a read/write mix
- of requests, and read/write servers are much harder to combine.
- This is because though read-only data needs to be placed on each
- server only once, a write to any server has to be propagated to
- all servers so that future read requests to those servers return
- consistent results.
+ quickly take over quickly if the primary server fails (high
+ availability), or to allow several computers to serve the same
+ data (load balancing). Ideally, database servers could work
+ together seamlessly. Web servers serving static web pages can
+ be combined quite easily by merely load-balancing web requests
+ to multiple machines. In fact, read-only database servers can
+ be combined relatively easily too. Unfortunately, most database
+ servers have a read/write mix of requests, and read/write servers
+ are much harder to combine. This is because though read-only
+ data needs to be placed on each server only once, a write to any
+ server has to be propagated to all servers so that future read
+ requests to those servers return consistent results.
- This synchronization problem is the fundamental difficulty for servers
- working together. Because there is no single solution that eliminates
- the impact of the sync problem for all use cases, there are multiple
- solutions. Each solution addresses this problem in a different way, and
- minimizes its impact for a specific workload.
+ This synchronization problem is the fundamental difficulty for
+ servers working together. Because there is no single solution
+ that eliminates the impact of the sync problem for all use cases,
+ there are multiple solutions. Each solution addresses this
+ problem in a different way, and minimizes its impact for a specific
+ workload.