Most of us are familiar with the idea of a supplier offering back-up with off site replication. But this level of redundancy can be achieved with a lot of autonomy by very small operators or individuals if needed, and is a great way of delivering a robust solution. Here are some points to consider.

Multiple locations with HA requires a Layer 2 connection. Some companies operate fibre connections between there own separate DCs or you can arrange for this kind of connection from a provider and have more freedom to chose your own DCs. If you go over IP you will kill your budget. If you are mirroring a HA then it will already be costing you. But the benefits of off-site mirroring and geographical separation are numerous as listed (to name bus a few):
1. Separate T1 providers
2. Separate power grid feeds (think California or Spain..)
3. Separate geo/climate risks (Japan/New Orleans etc.)
4. Diversity if DC operator business failure
5. Reduced operating insurance premiums

Some companies will give you a good deal on all of the above. But be sure to check out managing three different companies - for more redundancy of course..

Nice concept However, I am not technically sound person so my usual question is how much it will cost to set up entire process that you've been explained.....

Mirroring off site would be very costly but can be done with dark fiber connections

find a colocation company who have multiple data centres linked by a dedicated layer 2 connection. they will give you space for a server or VPS on one site and a server or VPS at another with a e.g. 1Mbps cross connect. I would go up the food chain for this i.e. not just a hosting company but a data centre operator or at least a hosting provider that has layer 2 services to another DC. however, if you try to chose two different companies, there may be a charge cabling and routing to the other provider (are you with me?) The larger the company is (hopefully) less likely to go our of business and the will bundle all the networking/cabling costs in cos it is cheaper for them - you are already on their network so no need to do anything. You can then implement the virtual software that allows for HA configs, such as ESXi - I am no expert here - try other forums for a good answer on specific HA and cluster OSs

I don't think it is practically that much sound, because it will raise the cost of server mirroring set up or configuration very high. As we also offer server mirroring solution, BUT we set up load balancing solution in one DC only. You are recommending to opt multiple locations, in this case how could it be possible to move services and application IP within servers who are located at different Data centers.

Funny you bring up off-site mirroring, as we'd been looking into it. It's one of those things that can be done, but it's a matter of cost, not a matter of potential. The costs involved with that would demand significantly higher pricing, and many clients will naturally object to that.

Many Hosting companies provide Mirroring solutions on Dedicated servers. These companies have different DC's. So the 2 servers used in the Mirroring setup are located in different DC. The location can vary depending upon the DC's which the Hosting provider has. He might have multiple DC's in the same country or he might have a DC in a different country. You can inquire about the location and choose your preferred location if Hosting provider has multiple options. Having setup servers in different DC's means you have FT(Fault Tolerance) and as its setup using Dedicated servers, you will have enough resources available. This solution offers 100% uptime as your data will be mirrored on both the servers in real time. So if the master server goes down due to any power or network outage in the DC, the slave server will become active and your websites will be accessible from the Slave server. Data will be continuously mirrored between the two servers, so once the Master server comes up it will take control.

If you opt for a Offsite backup, you can ask the hosting provider if the backup server is in the same DC or at different location. So even if the geo-location of the DC suffers from some any disaster like fire or natural calamity like Earthquake, your data will be safe on backup server which is in a different location.

Both Mirroring and offsite backups can be used to secure your data, but both work differently. Mirroring solution offers you 100% guaranteed uptime and secures your data while Offsite backups only secures your data. You can choose any solution depending upon your requirements and budget.

For redundancy purpose it is better to opt for a mirrorring solution. With mirroring you will have real time back-up with you. In case you feel that mirroring is expensive, in that case you can opt for off-site back-ups.
Some people, who have very important data on their servers prefer opting for both mirroring as well as offsite back-ups.

somewhat I agree with you James-A, but can you elaborate the key requirements for load distribution among two or more dedicated servers between different data centers?