Someone once said that a web application is truelly scalable if all one needs to do is to buy more machines. This is very appealing to me. Imagine you start a website, first with one box containing both the web server and database server; then as your users grow, you just add servers and load balancers; and eventually you add data centers (host in both west and east coast, europe, etc.) Ideally this should be done in a high availability fashion.

My question is what are the main design decisions to accomplish this? (e.g., not storing anything in sessions?, but load balancers can be sticky), cluster of webserver and database servers? how does database replication/synchronization work across data centers (how fast and how expensive?) How does the big boys (google, yahoo, ebay, amazon etc.) accomplish their scalability? Anything special about Perl/mod_perl one can use or needs to be careful about? Thanks.

In reply to Hardware scalable web architecture by theshz

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.