I'm running a large blog that is increasingly finding that it is outgrowing a single server. At present, load on the main server is cached with a varnish front end, but when users hit a large breadth of pages, the server is reaching capacity, causing editors using the admin panel to suffer.
I am working toward splitting our wordpress install into a load-balancing scenario, and making preparations so that these systems can have a read only environment with some sort of mechanism for synching the files (probably lsyncd).
So my big question is it possible to move the wordpress admin functions to a separate server, so as to guarantee Quality of Service for the writers of the blog, no matter what the traffic load is to the public site? As I am sure everyone here is aware, cloning the site to a separate server but sharing a database doesn't work, because the new "admin site" finds the rewrite rules in the database and wordpress redirects the user login to the public site.
This has a couple of sub questions, I suppose:
1. Is there any quick way around the built in redirect? Sometimes one just desperately wants this maintenance reasons. I'd be great to just put in a few lines of code in wp-admin.php, perhaps by accessing the admin panel on a separate port or URL and thereby have all traffic for the admin panel go to the admin server.
2. Is this something that multi-site plus domain mapping can make work? I started to look into setting up a system where site A would be publicblog.com and site b would admin.publicblog.com, but it seems that the nature of subdomaining on the WP network function is really that of having multiple vhosts/domains on the same physical machine with one login. I want the opposite: I want to have a separate site B, on a separate server than A, with SSL etc. that updates the posts on Site A.
Those are my core questions. Ancilliary to these might be:
1 Is it hard coded into wordpress such that the site URL and the admin URL must be the same?
2. Is there a "recommended" way to make wordpress work in a load-balancing environment. I see people creating a read-only file system and forcing media files to upload to Amazon S3. But what about plugins and themes? Do people sync those files (behind the back of wordpress) using the file system or is there a way to do this using the multisite functions?
Thanks for any suggestions!