High availability on remote site

[Olivier Nicole]

Hi,

I have been assigned to offer HA on a 3 tiers architecture.

Data storage tier will be MySQL, so replication is easy.

HA should be implemented only on the Data storage tier, Active/Active,
but one of the sites is remote!

When everything is working, each application accesses the local MySQL
tier, but when the local MySQL becomes unavailable, it should be able
to automatically move to the other database server.

I have no access to the application, so I cannot modify it to test if
local MySQL is working. So I should have an HA mechanism that enforces
changing the IP address on the database server.

If both servers are installed at different places, with different
addresses, would there be a way beside establishing an IP tunnel/VPN
between both places to have all machines in a single subnet?

An image is here http://www.cs.ait.ac.th/~on/HA.gif

I am really bothered by the IP tunnel, but that's the only way I see to keep HA.

Any idea welcome.

best regards,

Olivier