Re:No difference, just a matter of packaging. (Score 1)

I agree with TheMohel: There is NO DIFFERENCE between Server Clustering and Fault-Tolerant Servers. The only difference is "a matter of packaging"... or in my words, a matter of WHERE a level of redundancy is implemented.

The main issues concern 100% Uptime, Server Performance, and Data Safety. It is the IT Manager JOB to [1]Imagine all worst case scenarios, [2]Employ a solution which protects against those scenarios, and [3]routinely exercise his/her system's redundant solution to verify it's actual redundancy.

I want to avoid being technical, because 100 years from now systems will be completely different, but the question of WHERE to employ redundancy will always be important. So many people here are making arguments that there Clustering System doesn't even work, blah blah. News Flash: If your Clustering System doesn't work, IT'S NOT A CLUSTER! If your Fault-Tolerant server experiences a Fault, IT'S NOT FAULT-TOLERANT.

A Wise (Good) IT Manager will always routinely test there system to make sure it works. So now a wise IT manager knows he/she needs to focus on what his/her systems vulnerabilities are. For example, I remember a while ago microsoft.com experience a DNOS attack and was down for a day or so. There weakness? Their server farm, which even if it employed both Clustered and Fault-Tolerant Servers, failed because it was all centralized in Washington. Now they have another server farm somewhere else, providing them with redundancy against a DNOS attack.

But who cares about MS's uptime... more important systems exist like air traffic control, nuclear power plant systems, banks, government, etc.

A Wise IT Manager will see that what they really need to identify is WHERE redundancy is needed. Server Clusters can provide redundancy on a Server level, on a ISP level, on a power-grid level, and on a geographical level. Fault-Tolerant Servers provide redundancy on a hardware or software level, whether it be CPU's, Disk Controllers, Hard-Drives, and Power Supplies or Virtual Computers, Databases, or Applications.

I remember reading a powerpoint overhead I got from MIT's OpenCourseWare... one of their computer science classes. The one that "stuck" with me said something like:

"Systems are ephemeral, but Data is eternal"

I had to look up the word ephemeral, but it means "short lived." And this is very true. Whether we store Romeo & Juliet in Shakespeares original hand-written form, or typed with a type-writer, or stored in binary on some database somewhere, the PRESERVATION of the DATA ITSELF is what is important. The SYSTEM ITSELF is not so important because it will eventually change... according to Moore's Law. The only issue concerning the system is it's ability to preserve and serve the Data.

-Tony