Why is Google indexing & displaying www1 versions of my site and how might I stop this?
My answer to Why is Google indexing & displaying www1 versions of my site and how might I stop this? on Quora
You should stop serving your site to the public on multiple subdomains. Configure your site to serve a 301 permanent redirect from www1-www4 to the equivalent page on www—also, make sure that your site accessed without the www redirects to the right place as well.
The use of 301s will avoid any SEO penalty.
Why should you take this relatively extreme measure? Because serving on multiple subdomains hurts you in a bunch if ways:
1) Your SEO is spread across multiple copies of the same page, hurting your page rank.
2) Your cookies may end up spread across multiple domains, hurting your analytics and resulting in frustrated users who are signed in on only some of your subdomains
3) You’re damaging your scores on social media sharing sites. To use quite an old example, delicious used to use the number of bookmarks to a unique URL to decide what would appear on their “popular” page. Having multiple URLs for a piece of content split that score, making it much less likely you would appear there.
4) You’re making life harder for yourself should you need to switch to serving your entire site over SSL (which you may need to do to see Google search referral information as they move more of their search results pages to SSL)
Using rel=canonical is a good short-term fix, but it’s not too hate to implement the proper 301 fix and in my opinion it’s well worth the effort.