3 ms·

What, from a black box perspective (i.e. performance, reliability, cost/compute, maintenance-cost/compute) distinguishes a modern mainframe from a modern onsite

by danans 6y ago

What, from a black box perspective (i.e. performance, reliability, cost/compute, maintenance-cost/compute) distinguishes a modern mainframe from a modern onsite private compute cluster? Let's say both are running the same OS and application using VMs, and neither is doit specialized types of compute (i.e GPU stuff), just processing gobs of transactions. Obviously there are big internal architectural differences, but ultimately these must manifest in some quantitative and qualitative differences and tradeoffs from a black box perspective. Please discuss.

marcosdumay 6y ago
You want to know from what point of view? From the buying manager POV, one is cheap commodity and the other is expensive single vendor equipment. From the programmer POV, one is a proprietary environment with uniformly addressable memory (not UMA, just addresses) and the other is a distributed blank canvas where you must write the IPC yourself (or use a library, of course). Both have a huge IO capacity, but mainframes can integrate data much faster (and usually, process it much slower). From the ops POV, one is a single machine (a heavy one), and the other is an entire datacenter.
shrubble 6y ago
First point: it's not a cluster. It's a single server with massive amounts of cache (like 1Gbyte or more of the L3 cache) and optimized everything. When you login via ssh to your server, each keypress creates an interrupt which is handled by the CPU. If you are using emacs , even on the terminal it might be multiple interrupts due to screen refresh etc. Mainframe: generate the form or the screen data. Send it. 1 interrupt. Your terminal or terminal program handles everything until you send 1 or more lines (not characters) back. A dedicated processor handles communication with the terminal. It then bundles up whatever the changes are and sends it to the CPU. 1 interrupt. Disk, network etc. is the same, with dedicated processors on the network card or disk controller that go out and send/retrieve the data without CPU intervention. Database table retrieval: the table is sent to the CPU, already sorted in the requested order. Etc etc.

by danans 6y ago

marcosdumay 6y ago

You want to know from what point of view? From the buying manager POV, one is cheap commodity and the other is expensive single vendor equipment. From the programmer POV, one is a proprietary environment with uniformly addressable memory (not UMA, just addresses) and the other is a distributed blank canvas where you must write the IPC yourself (or use a library, of course). Both have a huge IO capacity, but mainframes can integrate data much faster (and usually, process it much slower). From the ops POV, one is a single machine (a heavy one), and the other is an entire datacenter.

shrubble 6y ago

First point: it's not a cluster. It's a single server with massive amounts of cache (like 1Gbyte or more of the L3 cache) and optimized everything. When you login via ssh to your server, each keypress creates an interrupt which is handled by the CPU. If you are using emacs , even on the terminal it might be multiple interrupts due to screen refresh etc. Mainframe: generate the form or the screen data. Send it. 1 interrupt. Your terminal or terminal program handles everything until you send 1 or more lines (not characters) back. A dedicated processor handles communication with the terminal. It then bundles up whatever the changes are and sends it to the CPU. 1 interrupt. Disk, network etc. is the same, with dedicated processors on the network card or disk controller that go out and send/retrieve the data without CPU intervention. Database table retrieval: the table is sent to the CPU, already sorted in the requested order. Etc etc.