Did some more reading and came across a comment by Ned Scott in another thread.
Quote:If you add a movie to the library to one XBMC instance and it does not show up on another XBMC instance, then they are not using the same MySQL library, or are not using MySQL at all. When MySQL databases are used, it is impossible to have a different library across XBMC instances. No exporting is required to add a movie. [b]You only need to update the library, just as you would for a normal local database.[b] Without debug logs, I cannot tell you why it doesn't work for you.
You see, my workflow at the moment is to Scrape/update the library on my i5 Win7 machine. It does this very fast. I then Go to the Video menu and "Export as separate files" and telling it not to overwrite so only the new stuff gets exported. This puts all the artwork and nfo's along side the media. The i5 machine also does this very fast. The other devices in the house are set to update library on bootup. They find the new stuff, find the nfo's and artwork.
Its probably a combination of slow old Nas' (2x Dlink DNS323's) and Slow Atom D525 CPU's in the Arctic MC001 XBMC clients but even with the clients not having to scrape nfo's or artwork from the internet, the library updates on the clients are slow and the client GUI's are slow while the update is running.
I thought using mySQL would solve this. That it would be like UPNP sharing where the uptodate library appears instantly on the clients when you turn them on without any need to update the client library. However from Ned Scotts comment above it sounds like I still have to update libraries on the clients. Thats the part I wanted to do away with by using mySQL!! Or did he mean you update the library on the master machine like you would for its local library, then the mySQL db feeds that to the rest of the clients instantaneously such that the client machines have their auto update settings turned off.
If its the former rather than the latter interpretation then in effect, is MySQL merely automating the workflow I already use. ie Scraping and updating library on one machine, exporting the NFO's and artwork to the media folders. Then the clients scraping/updating from this Nas-local nfo's/artwork instead of going on the internet.
If thats the case then it turns out that UPNP sharing is closer to what I want/need. The only problem with UPNP sharing for me at the moment is that it doesn't seem to share the extra fanart, clearart, logo's and disc art etc. Is that coming with UPNP sharing on Gotham? I'll just have to wait for it to go gold though as I can't use the nightlies as I am using openelec on the clients, so have to wait till openelec switches to gotham.