What are Mainframes?

I remember a network manager telling me the drives on one of our servers were 'hot swappable'. I explained that this was not the case - standing next to me in the server room he said 'look if I pull this disk out the network will stay up'. I spent the next day rebuilding the database he corrupted and the business was without IT systems for the day.

As a mainframe COBOL programmer I greatly appreciate this video! Yes, I was born after 1980.

Wonderful and accurate. I've been working on this type of IBM system for 35 years now. This guy "gets them". There are even more redundancies than he mentioned. Automatic cpu recovery, if a CPU fails, a spare takes over and the instruction which died is automatically restarted and the user software doesn't even know it. Same with RAM memory.

Did you know you can break into any mainframe by typing super fast into a green command prompt while techno music plays? It's a law of nature. Abraham Lincoln wrote an essay on it.

3:40 the lady's hand aligns with eye

I have 10 years+ developer experience on IBM mainframes. And I kind of miss the old days. For instance - back then, pressing F3 to save whatever sourcefile I was editing it usually took <1 second to save and when the system was slow maybe 3 seconds. These days saving my work to "the very large and popular cloudbased CRM system" takes 3 seconds if everything is miraculously fast - but a 30 second wait is normal.

"Big Iron" just reminds me of the Fallout: New Vegas soundtrack.

I once visited the IBM datacenter in Böblingen, Germany. It was a truly impressive experience to see hundreds of IBM z13's all together in one big server room. These were probably the most expensive things I've ever seen in one place!

Linus when I hear "big iron" I think a heavy caliber six shooter.

z16 is now coming out with the Telum processor, my job as a COBOL programmer has never been more secure

And here I thought I knew what mainframes were.

For the IBM Mainframe affectionados out there. IBM announced the Z15 system, some specs are: up to 40 terabytes (TB) of RAM, up to 1536 I/O channels with over 600 FiConn channels (optical), up to 190 user processors (UP) each with 12 cores at 5.8 GHz, and a slew of specialty processors. The level of complexity can only be described as mind boggling.

As a former IBM SSR, I'm thankful you did a video on this @Linus, I wish more people took interest in enterprise systems like Z. Short and Quick summary, but informative for the length. Thanks!

As a mainframe system programmer, thanks for clearing up many of the misconceptions and explaining what a mainframe really is so people are better informed :) z/OS FTW :)

"mainframes aren't designed to run games" next up on linus tech tips "1 million dollar main frame smashed in super mario brothers emulator benchmarks by raspberry pi"

Thanks for being mostly correct (latest IBM is the z14 ;-) ). When I hear "Big Iron" I think of a very satisfying 46 year career.

but, can they run crysis?

Seriously, one of your best videos to date. I thought everyone forgot about Mainframes. Kudos for the topic.

Thank you for posting this. As a mainframe systems programmer with over 30 years experience it is nice to see someone with some understanding of what mainframes do. One thing that should be mentioned is that IBM's large systems operating system Z/OS is setup so that it can be 'plexed' together. You can have multiple Z/OS images running across multiple mainframes that are connected in a 'SYSPLEX'. If one system or even one processor is taken down for maintenance the other systems will take up the slack and continue on without the end user even knowing what is going on. Also mainframes do not have internal disk storage. The mainframe is connected to a external storage subsystem like an IBM DS8000 series unit. The disk system is also redundant so that if one of the drives fails it will automatically recover onto another disk drive. The storage subsystem can also be setup so that it takes advantage of asynchronous write. This is where data is written to the the local disk unit as well as an offsite unit at the same time. The disk subsystem can also be encrypted so that all the stored data is totally encrypted at all times.

Cool video. I started as a Cobol programmer on IBM Mainframes in 1979 and worked my way up to Technical Specialist at IBM. Cobol, CICS, DB2, IMS. Left the business in 2004 to do something completely different after working for a major UK retailers on a system that ran over several mainframes and spent all day working out what people will buy in the next 21 days.