I can fit 4 C7000 chassis in a single rack, which top out at an aggregate 32 TB of memory and over 2000 cores. 5 GHz cores running s390x microcode are not, FYI, twice as fast as Xeons.
It would be great if people who weren't familiar with the state of the art in x86 kit didn't blindly assume IBM et al's advertising was reality.
I'm no expert, but my understanding is that the IBM "z" platform has a number of interesting features perhaps not found in more typical server platforms/configurations, beyond just scaling out to loads of cores and RAM.
As with all IBM mainframes going right back to the 60s, the "z" systems are designed for continuous uptime, on the order of decades, and this is evident in many of the design decisions. For example, various subsystems and components have hot-spares available, so that even outright component failures will not cause downtime. Many components are then hot-swappable, even those that might not ordinarily be in other architectures, such as processors and main memory. No interruption to OS or application-level services is expected by hot-swapping such hardware. Across the useful life of the mainframe, most repairs and maintenance would be carried out without ever shutting it down.
I understand the platform also has extensive internal integrity checking built in, a potentially important factor for various types of jobs. Its auditing service is capable of detecting unusual conditions in various subsystems or jobs ("I've just picked up a fault in the AE-35 unit"), automatically retrying instructions on the processor if they executed anomalously. If the fault continues, the suspect processor is routed-around with no interruption to OS or applications, the job is resumed from last checkpoint on another processor, and the system phones home to IBM to log a service call. This monitoring is not being performed by processes running in userland or by the kernel, but is in fact baked into the hardware/firmware platform.
Furthermore, the systems can be configured with a variety of specialty offload processors or subsystems for tasks like encryption, key management, compression, and even logging -- which again might not be so commonly found on-board of some commodity servers.
(And, of course, even if you could put together an analogous solution with commodity kit, it's IBM! For the sorts of companies looking at a mainframe in 2015, having the IBM name on the SLA has got to be a pretty big part of the equation, right?)
Moreover, if you proposed to build and manage these sorts of capabilities from commodity x86 kit, I imagine IBM would claim that they'd have the lower TCO.
Whereas I have hands on experience with this stuff. So I guess I should thank you for giving me first-hand experience of being on the receiving end of that mansplaining thing people complain about.
> I imagine IBM would claim that they'd have the lower TCO.
Yes, they will. The funny thing is, the man from HP was in just last month explaining to me that Xeon Superdomes have a lower TCO, too, and last year the lady from Oracle was telling me how I shouldn't balk at the headline cost of ExaData and ExaLogic because, from a TCO perspective, they'd save me money.
People fall into the mistake of just comparing cores and memory specs between x86_64 and s390x. The hardware redundancy benefits are pretty huge. You really need a full proof-of-concept to get any picture of how your workload might run on System z.
NB your AE-35 comment, despite loud protestations there's a very good case that 2001 was written and directed as a sharp critique on IBM. Including IBM logos in numerous places.
No. Which workloads do you have that need more than 40 cores per image, are happy with a maximum of a hundred on, and won't run on clusters? (I hope it's not one that's going to be crippled by zVM's slow scan of large memory areas suspending guest execution).
> I/O offloaded
If you've actually worked with zLinux (I have) you'll know there's little effective offload, and that zVM overhead increases as the virtual IO ramps up.
> and five 9's
Is zVM offering sysplex? No. So you're relying on your single LPAR to be five nines? Never upgrading zVM? Never updating PR/SM?
Is the datacentre five 9s? The power? The network? Really?
I can fit 4 C7000 chassis in a single rack, which top out at an aggregate 32 TB of memory and over 2000 cores. 5 GHz cores running s390x microcode are not, FYI, twice as fast as Xeons.
It would be great if people who weren't familiar with the state of the art in x86 kit didn't blindly assume IBM et al's advertising was reality.