Sharing thumbnails between 2 XBMCs

Hi!
I have 2 XBMCs running. One is a HTPC with Debian Wheezy (amd64), the other is a Raspberry Pi
with Raspbian. Both have Frodo from git self compiled, the same version.
I want to share the video and music library, so I have set up mysql on my home server.
First I exported the video db from the HTPC into a single file. After that I set up both machines
using mysql for the video and music db. I also deleted Textures13.db on both. I set up a nfs share
for the Thumbnails and the playlists folder on the home server, and created symlinks in my
userdata folder to this 2 folders. The permissions are also correct.
After that I imported the videodb from my HTPC. The db was successfully created and the thumbnails
also landed on the nfs share.
Testing from the HTPC, everything is fine, except the movie sets had to be set up again. Maybe these
settings are not ex / imported.
But the Raspberry only shows a working db. The library is ok, and also the watched state is correct.
But it does not show any thumbnails. Textures13.db is created, but it is very small. I tried again, deleting
this file, but it is created as before. Then I copied the file from the HTPC to the Pi. Now the graphics are
shown. But I am not sure, if this was the right way, if future library updates from the HTPC show the
graphics on the Pi.
The log does not show anything about this.
Did I go wrong somewhere? Can I also move the Textures db to mysql?