Subdomains versus subdirectories

What are the advantages and disadvantages?

[Webwork]

Is there less CPU overhead resolving to a subdirectory versus a subdomain?

Is sub-dir versus sub-dom "proven" to be more search engine friendly?

Is updating a website, based upon subdomain versus subdirectory any easier or more difficult?

If a sub-domain gets hit with a penalty does it kill the parent domain?

What is sections of a sub-directory were, to whatever degree, duplicate content? If that only applied to one sub-directory but not others what then?

I'm looking at website network design issues and need to make a choice: subdomains versus subdirectories, so I'm going on an issue spotting expedition.

Bring on the wildlife.

[jhussher]

Well I know for me it is easier to update pages with different subdomains, that is how I have Macromedia Dreamweaver set up. I treat each sub dom as a separate site. It then has its own tree of subdirectories. And I then treat some of those subdirectories as separate Dreamweaver upload sites.

[wackybrit]

Is there less CPU overhead resolving to a subdirectory versus a subdomain?

Any overhead would be neglibile, but the answer is 'yes', although much of this depends whether you host your own DNS or not.

If a visitor is on your main site, then goes to a subdomain, this requires another DNS lookup, which, if the DNS server is on the same machine as your site, would add a few hundred bytes more load to events ;-) This factor is not really worth considering though.

Depending your server arrangement, subdomains can be very easy to manage. You can have it so that subdomains dynamically go to a certain subdirectory on your Web space.. so subdomain1.widgets.com could go to /home/yourwebspace/subdomain1.widgets.com/ and so on.

[jamesa]

To the best of my knowledge, Webwork, subdomains will usually be seen as separate domains whereas subfolders will almost never get that distinction.

CPU overhead should be negligible. On the server you can either set up a subdomain as you would a separate site, or you could use a mod rewrite to point the subdomain to a subfolder of the parent (or any other) site. A link to a subdomain (vs a relative link to a subfolder) will initiate a seperate DNS lookup - subdomains can be on different IPs - but that should be minor.

Sub domains were designed as another branch in the domain system. The registrars delegate domain names to site owners like us. We in turn can delegate our sub-domains to other webmasters in the same way. Subdomains can be hosted on completely different servers in diiferent parts of the world, have different name servers, different mail servers, etc.

HTH

P.S. - There's a lot of info on this in the link development forum, especially Paynt's threads from a while back.