>but a pure Linux mainframe is surprisingly competitive not just in compute and throughput but also in pricing.
It's not competitive when you consider what long-time IBM mainframe customers actually do. E.g. SABRE airline and travel reservation system was one of the first IBM mainframe customers in 1960 with the IBM 7090 and then upgraded to System 360 and then the newer Z mainframes. SABRE's multi-decade experience with IBM mainframes with mission-critical business applications means they are one of the world's foremost experts on its capabilities & costs that's not biased by any IBM marketing or sales pitches.
Even with all that in-house experience, SABRE still chose to gradually migrate off of IBM mainframes to less expensive tech stacks. Some have touted IBM's TPF (Transaction Processing Facility) on the mainframe as compelling technology but that still didn't dissuade SABRE in ~2001 when they migrated the airfare pricing application to Tandem (Compaq/HP) NonStop servers running UNIX. (https://www.computerworld.com/article/1339621/has-mainframe-...)
> We moved 93% of compute capacity from physical data centers to the public cloud, resulting in a 50% decrease in our compute costs.
> We migrated more than 120 million bookings from a mainframe-based system to one using Google Cloud’s Spanner database, without impacting customer operations.
JP Morgan Bank is another example of migrating from IBM mainframes to cloud. If anyone out there truly thinks that running a new greenfield Linux workload will be be cheaper or even cost-competitive on a new IBM Z mainframe, just pause and consider if you truly know something about IBM mainframes' OpEx that multi-decade IBM customers like SABRE and JP Morgan don't already know.
Why would any new customers in 2025 willingly buy into IBM Z mainframes if they see existing customers spending billions trying trying to move off of them?
I’ve had to budget a line of business app that runs on both z/OS and AWS. Reliability for both hit an asymptote somewhere around 2019. The opex price crossover happened somewhere around the same time, depending on the customer.
Nearly every installation site and their internal support director agrees that the z/OS installations are far less expensive to support, simply because the minimum level of experience for a z/OS engineer is about a magnitude more than a cloud engineer.
It's not competitive when you consider what long-time IBM mainframe customers actually do. E.g. SABRE airline and travel reservation system was one of the first IBM mainframe customers in 1960 with the IBM 7090 and then upgraded to System 360 and then the newer Z mainframes. SABRE's multi-decade experience with IBM mainframes with mission-critical business applications means they are one of the world's foremost experts on its capabilities & costs that's not biased by any IBM marketing or sales pitches.
Even with all that in-house experience, SABRE still chose to gradually migrate off of IBM mainframes to less expensive tech stacks. Some have touted IBM's TPF (Transaction Processing Facility) on the mainframe as compelling technology but that still didn't dissuade SABRE in ~2001 when they migrated the airfare pricing application to Tandem (Compaq/HP) NonStop servers running UNIX. (https://www.computerworld.com/article/1339621/has-mainframe-...)
They then started a 10+ year effort to migrate more mainframe workloads to Google Cloud. E.g. from https://www.sabre.com/insights/a-journey-to-tackle-legacy-co... :
> We moved 93% of compute capacity from physical data centers to the public cloud, resulting in a 50% decrease in our compute costs.
> We migrated more than 120 million bookings from a mainframe-based system to one using Google Cloud’s Spanner database, without impacting customer operations.
JP Morgan Bank is another example of migrating from IBM mainframes to cloud. If anyone out there truly thinks that running a new greenfield Linux workload will be be cheaper or even cost-competitive on a new IBM Z mainframe, just pause and consider if you truly know something about IBM mainframes' OpEx that multi-decade IBM customers like SABRE and JP Morgan don't already know.
Why would any new customers in 2025 willingly buy into IBM Z mainframes if they see existing customers spending billions trying trying to move off of them?