I have the following setup: two WordPress blogs, one on the main domain, let’s call it example.com and one on a sub-domain sub.example.com. After a few years of running these blogs independently I have to merge the sub-domain into the main domain:

sub.example.com > example.com

Each blog’s database is over 100MB and the sub-domain uploads folder is over ~15GB (lots of high-res images). Both blogs have the same authors and only 2 common categories.

What’s the best (safest) way of doing the merge to ensure that everything runs properly?

These are the steps I considered:

1. Backup each database;
2. Optimize each database;
3. Backup again;
4. Export XML from sub.example.com;
5. Move the contents of sub.example.com/wp-content/uploads/ to example.com/wp-content/uploads/ – (and hope there are no files identically named);
6. Import XML into example.com;
7. Create .htaccess file on sub.example.com to 301 redirect all to example.com;

The only step I’m not sure is #5, should I move (merge) the uploads folders or let the import process handle this as well? I’m thinking that since it’s 10 GB worth of images the import process might fail…

If anyone has a better process or if you see a problem with one of the steps from above, let me know, I’ll appreciate any help on this matter!