You will have the best success with a remote desktop / terminal server type connection from one or both sites.

The tcp/ip communication to and from the Database Daemon will sort of work, but the latency is high.  

The connection from the MySQL database daemon through to disk storage has to be a direct disk connection (or iSCSI, which is also a disk connection).   Nothing else will work.

This does not make any sense. MySQL is the largest database engine out there and I'm sure many companies are using VPN connections to write to databases. There has to be a liable solution out there somewhere.

I had a prospective client call yesterday or the day before about the same concept.  I essentially recommended the same type of solution Randy suggests, remote control as the best option.  However, it looks like you already have a VPN set up so it would be easier for you to test.  I tested the VPN connection on my own server from a hotel I was staying at a few years ago, and it took enough time to open the file, for me to go downstairs, grab a coffee and go back to my room using the stairs (one floor).

Getting information from drop-downs, etc. and posting were also delayed.  One customer invoice can hit over 20 tables when posting so it does take time.  Now was I delayed because I was using a hotel wireless setup or because my own server is not set up correctly for VPN, I don't know.

First, get the database out of My Documents.  Even if you leave it on his computer, it shouldn't be stored there, especially with server redirects.

However, to test the VPN connection just take a copy of the file and set it up for access from both locations on your setup.  Let them both do some typical data entry simultaneously and you as a group be the judges if it works or not.  Make sure you are on the phone together and do some of the same things at the same time to see what kind of delay there might be between using the system at each location.

I would not be surprised if the distance location is slower.  However, I am pretty sure there would be a lot of people here interested in your results.  Test things like the speed for:

1. Opening the file to the Home Screen.
2. Opening the sales data entry screen
3. Selecting a customer
4. Posting a typical 2 line invoice with inventory items and projects if applicable
5. Running the Customer A/R Aged Report
6. Running the Inventory Transaction Detail report if applicable
7. Close the file at both locations, count to 20 to let the MySQL process close on the server and reopen only at the distance location
8. Do the same as #7 but at the office location where the file is located
9. etc.

I am in the process of moving the database to just a regular share and set it up so that only one security group can access the database. When I have an update on that, I will let you know.

I should also point out, that my server is not the one handling the VPN traffic. I use two Watchguard XTM 26's to handle all that so there is a constant connection between the two locations. the speed between the two buildings are actually pretty good. Can transfer files at a pretty good rate (don't recall what it is exactly).

When I have more details on the test, I will let you know.

Alot of this discussion is beyond my IT skills, but I will share my experience with VPN. It sucks for writing to databases. I sometimes have to access a large database, but since I often have delay glitches with the VPN, I try really, really hard to schedule my time so that when I need to actually do writes to the database, I can do so onsite, rather than through VPN. I`ve basically given up on VPN for database writes.