The simplest Slash installation features one site running on one web server. This is not a limitation of the software. Thanks to advanced features of Apache and the Perl DBI modules, as well as clever coding, Slash can be used to run several smaller sites on one machine (in a managed hosting situation, perhaps), as well as one large site served by several machines. It’s even possible to mix the two configurations.
Because it was designed to run Slashdot, the Slash software is scalable from a single machine to large web site clusters. Based on the level of traffic you expect, you can choose from several possible server configurations. Most new sites start with low requirements and can live comfortably on a single, properly tuned machine. Figure 2-2 shows other available options. Putting the database on a separate machine, connected via a high-speed network, will alleviate some processing and memory crunch.
Figure 2-2. Several possible Slash configurations, scaling with the expected web traffic
Larger sites might run several web servers with a single database. In this case, the individual servers would mount an NFS directory served by one machine (which may or may not itself be a web server), and access a database on another machine. This is the configuration Slashdot itself uses. For extremely high traffic sites, it’s possible to use ...