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What are the advantages of these mainframe systems versus a basic Linux server?

• skissane 4y ago
  Backward compatibility. In 1970, you buy an IBM mainframe and start writing apps to run on it. In 2023, you are still running the same code base - albeit with innumerable enhancements and fixes over the ensuing decades. On an IBM mainframe, that code base will just work. On Linux, it won’t even run - unless you buy some expensive mainframe rehosting package, which is full of gaps and limitations, and may introduce obscure bugs which the original lacked. Reliability - most large-scale Linux systems are based on a distributed model - the app runs on a cluster containing dozens/hundreds/thousands of servers, if a single server has a hardware fault, the app just keeps on working and at worst some user might get an error which goes away if they retry. So, no point in spending $$$$ to maximise the reliability of any individual node. By contrast, many mainframe customers have just one mainframe, and if it breaks they go down - which means the mainframe hardware has to be super-reliable, filled with redundancy, error detection/recovery, etc - and you pay $$$$ for all that redundancy. IBM mainframes can be clustered - e.g. z/OS Parallel Sysplex - but only the largest sites do that. The maximum supported cluster size is 32 - I wonder if anyone actually runs one that big, 32 mainframes would be horrendously expensive - while Linux clusters with hundreds or thousands of nodes are quite common.