I'm making a fairly large (for me) e-commerce shop with Woocommerce. The shop has ±1300 products and will be going to ±2000 products. There are also ±2500 Product Tags.
I've had speed problems on a shared hosting server; updating posts took over 1 or 2 minutes from time to time. The front-end of the website has always been really speedy.
So I've moved the server to a VPS server with 2 processor cores of 2.3Ghza and 2048 Mb Ram. There's no visitors on the website; no traffic problems. As said before, the front-end is really snappy. Every pages loads in under two seconds.
However, certain things are really slow in the dashboard/admin of WordPress. Everything in the dashboard is really quick and responsive. Changing from posts to pages, to settings, to listing products in Woocommerce: all very snappy.
Updating products is quick when changing the_content and adding text in custom fields. Every product has a lot of custom fields (≠50) that are served via the plugin Advanced Custom Fields. No problems there.
The BIG problem comes when I try to add 'Product Tags' (or any other term to a taxonomy where there are already 100-200+ registered terms). When I add one or more Product Tags, they appear quickly in the dashboard sidebar box. However, when I then try to Update the product, the spinning WordPress wheel keeps spinning forever. The website hangs. I can try to access another part of the WordPress dashboard, but it doesn't react anymore. Only restarting the browser helps.
There's also an important issue with the 'Product Tags' menu item under 'Products' in the sidebar. I tried to add tags from there, but it blocks the site as well in a different manner. I can fill out the field to add a Tag and than hit 'Add new product tag'. Then I get NO message whatsoever that the tag has been added... the text of the new tag stays in the text field too. The button can be clicked multiple times, but it looks like nothing ever happens. When I restart the browser, the new tag has been added though. I found it doesn't block the site; it just takes a really long time (+1 minute) and there's no progress indicator...
Plugins: 14 active. It doesn't change when I turn off all other plugins besides Woocommerce.
Could you please help me out? I've made several screencasts to explain the problems. http://support.woothemes.com/requests/20665