Any kind of forum software is server-intensive, especially if the forum houses a large community. Optimizing vBulletin can be helpful for busy forums or for those hosted on a shared server. If the following are done, your forums will definitely be faster and server load would be decreased.
1. Transfer Avatars, Images, and Attachments to the File System.
By default, all of the above are stored in MySQL. Database storage of these result in increased load and login I/O times. If they’re transferred to the file system, a lot of resources would be freed up. You can accomplish this by creating separate folders for them. Then, in the admin control panel go to Avatars > User Picture Storage Type and Attachments > Attachment Storage Type. Change their storage type according to the folders you created.
2. Transfer CSS to the File System.
vBulletin renders CSS stylesheets in each page’s header. Hence, this entire code is included in every page view and it needs to be redownloaded for every view. If you transfer CSS to the File System, bandwidth usage will decrease and pages will load faster. Go to vBulletin Options > Style and Language Options > Store CSS As File Sheets.
3. Control Spider Activity
To save on bandwidth, make a robots.txt file and place it in your site’s root for spiders to find. With this, spiders won’t crawl on irrelevant portions of your site that will do nothing to boost your search engine rankings.
4. Look at Your gzip Settings.
Gzip is a technology that compresses the data from your website to the web browser. Through it, transfer times and bandwidth usage can be reduced hence decreasing server load. If your server has gzip enabled, disable gzip in vBulletin or else response data will be double-compressed and make loading time suffer. Disable it here: vBulletin Options > Cookies and HTTP Header Options. Choose “No” for GZIP HTML Output and set Compression Level to 0.
The above tips are for administrators who wish to milk out vBulletin completely for better performance. But before you implement them, make sure to back up your server.