Using .htaccess to serve static files via a subdomain - performance

Question

Right, excuse my stupidity, I've looked through a load of examples on t'interweb but I don't think I've found what I'm looking for.
I have a website, photography.example.com is the main site but I also want to have another subdomain to serve static files, for example static.photography.example.com.
If I request a file (e.g. http://static.photography.example.com/js/jquery.js) I want that file to be retrieved from the non-static domain, allowing me to keep my file structure completely untouched but using multiple domains to allow more concurrent http requests.
I don't want to throw any http responses that would make the browser thing the file has been moved, I just want to mirror the files from the normal domain to the static domain. After this I would proceed to set far future expired to improve caching etc.
How do I achieve this using .htaccess?
EDIT 1
So after a bit of messing around I have come up with this:
Options +FollowSymlinks
RewriteEngine on
RewriteRule ^(.*)$ http://photography.example.com/$1 [L]
But this actually redirects to the domain I'm trying to read, I want it to serve the file up under the static domain name, any help with modifying this script would be greatly appreciated.
EDIT 2
So I've amended my DNS and waited a few days for it to propagate but the CNAME technique doesn't work either. Here's the entry:

Answer 1

In your question, you're talking about:
Adding Expire headers for caching
Splitting resources across domains
For Item #1, you can edit your httpd.conf/.htaccess file on your main domain (it doesn't hurt doing it on your whole website, no?)
<IfModule mod_expires.c>
ExpiresActive On
ExpiresByType application/x-javascript A2592000
ExpiresByType image/gif A2592000
ExpiresByType image/jpeg A2592000
ExpiresByType image/png A2592000
</IfModule>
Item #2 doesn't need any Apache configuration - just configure your static.photography.example.com DNS entry with CNAME photography.example.com. That should do the trick.
Or you can edit your httpd.conf and add a ServerAlias
<VirtualHost xx.xxx.xxx.xx:80>
DocumentRoot /
ServerName photography.example.com
ServerAlias static.photography.example.com
</VirtualHost>
So for now, you don't need a separate virtual host with dedicated Apache configuration.
Here are a few other reasons why you'd want a separate domain, and a separate virtual host with dedicated configuration:
Your main domain has cookies and you want to use a cookie-free domain
You actually want to use a CDN (or your Amazon S3 account to reduce bandwith on your primary hosting)
If you want one of those, or if your caching needs are too complex (you don't want to cache all JS/CSS/images, but rather a subset of it), then your only solution is: get your hands on your httpd.conf and write separate configurations for each domain

Answer 2

My understanding to the question is to REDIRECT
http://static.photography.example.com/js/jquery.js
to get the file from following address (without changing the URL on the browser):
http://photography.example.com/js/jquery.js
But keep URL to all existing files like the following to NOT REDIRECTED:
http://static.photography.example.com/images.jpg
If it is true then this .htaccess should work:
RewriteEngine on
RewriteCond %{HTTP_HOST} ^(.*)?.photography.example.com$ [NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*) http://photography.example.com/$1 [P]
Moreover you can also use MAPPING if you have a complex rules like:
RewriteRule ^/file1\.js$ http://photography.example.com/file.js?q=444 [P]
RewriteRule ^/file2\.js$ http://photography.example.com/file.js?q=345 [P]
RewriteRule ^/file3\.js$ http://photography.example.com/file.js?q=999 [P]
create a text document (e.g. map.txt) in the folder with .htaccess and put in the following:
file1 444
file2 345
file3 999
The .htaccess will have the following look:
# Set a variable ("map") to access map.txt from config
RewriteMap map txt:map.txt
# Use tolower function to convert string to lowercase
RewriteMap lower int:tolower
# Get requested file name
RewriteCond %{REQUEST_URI} ^/([^/.]+)\.js$ [NC]
# Seek file name in map-file
RewriteCond ${map:${lower:%1}|NOT_FOUND} !NOT_FOUND
# Perform rewriting if the record was found in map-file
RewriteRule .? http://photography.example.com/file.js?q=${map:${lower:%1}} [P]

Answer 3

I think you would need the CNAME record to pass the request for static.photography.example.com to your server and the have .htaccess parse requests for static.photography.example.com in a special manner.
Adding the following rewrite rule to .htaccess should do the trick
RewriteCond %{HTTP_HOST} !^(www\.)?photography.example.com$ [NC]