Can a mainframe do the work of a server?

Linux

Wow, that's a BIG question. Why? Because mainframes are very cutting edge computers (despite what the public might know from watching movies stuck in the past), but they also have a very long heritage that lets them continue to run programs and handle data from decades before PC computers were even invented (again, people see an old program running & often assume that's ALL mainframes can do).

The only really true mainframes today are IBM zSeries mainframes.

The short answer is just about anything any other computer can do.

Now, there are qualifiers to that. There are some things other types of computers can do better if you throw enough resources and power into those other types of computers.

HUGE DATA MOVERS -The first thing that comes to mind that mainframes REALLY do well is move huge amounts of data around efficiently. These days that's usually in the form of databases.

STAY UP FOR 40 YEARS OR SO IF YOU WANT - RELIABLE - What else can they do? Be VERY VERY reliable. I've been working with them for over a decade now (I do have a background in other types of systems, but I wanted something that wouldn't break while I was asleep or on vacation). NEVER in my career has a mainframe we have (or anyone at other companies in our area that have mainframes, for that matter) gone down because of a hardware or operating system problem. NEVER. Reliablity numbers continue to climb, but the oldest mainframe we have is rated for uptime over 99.9999999% uptime (i.e. about 40 years or so without a required reboot/ reIPL).

SCALE MASSIVELY - You've likely heard of "virtual machines"... well, mainframes are where that started. You can run thousands & thousands of vertual machines on one mainframe. You can connect mainframes together all over the place (they don't all have to be in the same place) to allow them to grow the resources used (but you need to understand that almost nobody needs more than one mainframe to handle workload... these things can scale capability within the single refrigerator sized mainframe). However, if you connected several together, you could roll workloads around in a way that users would NEVER have to see a system go down.

Linux - You might not know this, but Linux ROCKs on an IBM zSeries mainframe. Again, you could have thousands & thousands of virtual Linux servers on one refrigerator sized mainframe! You've likely had data served to you from a mainframe & never known it.

YESTERDAY, TODAY & TOMORROW - Mainframes are BACKWARD compatible. Stuff that was written when I was a baby STILL works & can be read on our systems (unlike many things I wrote on PCs in college that aren't in a currently supported format). New stuff of today also works on mainframes. This heritage is likely to continue into the future. If you have data you want to be readable in 40 years from now, mainframe is a good way to go.

MANY MANY MANY USERS ALL AT ONCE - There is NO other platform in the world that is as good at handling a LOT of users all at one time. There was a major financial firm that a consulting company talked into switching over to another platform. It worked just fine it testing.. there ARE other good platforms out there. However, in testing, they never had thousands of employees of a company all log on at the same time at the start of the workday. When THAT happened, the system became unresponsive. They switched back to their mainframe & never looked back. The mainframe can handle HUGE numbers of users & is VERY good at prioritizing workloads (so you can give more important workloads more resources).

I could go on, but I've got to go now. Perhaps I'll add more later. They REALLY are great machines, but it is a very rare person these days that gets to know these machines on a level to understand just how great they are!