Any large distributed system barely runs on the specific hardware/OS it was designed for and required constant monitoring and maintenance. Even OS upgrade (i.e. in theory it should stay compatible and "just work") in the large datacenter takes weeks of testing and fixing. Migrating from mainframe to linux is very very very expensive. On top of that to achieve same reliability there will be a need to re-architect some software pieces.
BTW, Google needs with MapReduce are fundamentally different - it favors scalability and thoughput over correcteness vs banks that need distributed transaction consistency most of all.
BTW, Google needs with MapReduce are fundamentally different - it favors scalability and thoughput over correcteness vs banks that need distributed transaction consistency most of all.