From f378ccc26155125414c0e050d464269f5ba2930e Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 1 Dec 2006 03:19:48 +0000 Subject: [PATCH] Minor wording improvements. --- doc/src/sgml/high-availability.sgml | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/doc/src/sgml/high-availability.sgml b/doc/src/sgml/high-availability.sgml index c2ea6a6d64..01d2c90207 100644 --- a/doc/src/sgml/high-availability.sgml +++ b/doc/src/sgml/high-availability.sgml @@ -1,4 +1,4 @@ - + High Availability and Load Balancing @@ -12,7 +12,7 @@ Database servers can work together to allow a second server to - quickly take over quickly if the primary server fails (high + 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 @@ -50,8 +50,8 @@ committed until all servers have committed the transaction. This guarantees that a failover will not lose any data and that all load-balanced servers will return consistent results no matter - which server is queried. Asynchronous updating has a delay between - the time of commit and its propagation to the other servers, + which server is queried. In contrast, asynchronous solutions allow some + delay between the time of a commit and its propagation to the other servers, opening the possibility that some transactions might be lost in the switch to a backup server, and that load balanced servers might return slightly stale results. Asynchronous communication @@ -101,7 +101,7 @@ standby server should never access the shared storage while the primary server is running. It is also possible to use some type of file system mirroring to keep the standby server - current, but the mirroring must be done in a way that the + current, but the mirroring must be done in a way that ensures the standby server has a consistent copy of the file system. @@ -159,10 +159,10 @@ protocol to make nodes agree on a serializable transactional order. With statement-based replication middleware, a program intercepts - every SQL query and sends it to all servers. Each server - operates independently. Read-only queries can be sent to a - single server because there is no need for all servers to - process it. + every SQL query and sends it to one or all servers. Each server + operates independently. Read-write queries are sent to all servers, + while read-only queries can be sent to just one server, allowing + the read workload to be distributed.