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The Mainframe Still Lives!
coondoggie passed us a NetworkWorld blog post about the incredible rock-em-sock-em mainframe. Knocked frequently in recent years, the site notes that IBM's workhorse continues to do important work in a number of enterprise environments. "While there are some out there who'd like to see its demise, a true threat to the Big Iron has never really amounted to much. Even today, the proponents of commodity boxes offering less expensive x86/x64 or RISC technologies say the mainframe is doomed. But the facts say otherwise. For example, IBM recently said the mainframe has achieved three consecutive quarters of growth, marked by new customers choosing the platform for the first time and existing customers adding new workloads, such as Linux and Java applications."
Hardware quality is the key here. It may not matter, if the application is even 30% faster on x86. But if the motherboard is buggy, or the parallel port is flaky, or cable can fluctuate, or the video card can get loose (early AGPs anyone?) — it is death. Even if the probability of it ever happening is very low, the costs will be devastating. Thus the expectation (probabilty times cost) of the loss is still lower than the cost.
I've heard of machines, where the CPUs or memory can be replaced without shutting down — 15 years ago (Sequoia)... Meanwhile, some controllers and OSes still don't fully support hard-disk replacement, or even network cable unplugging — today...
In Soviet Washington the swamp drains you.
FYI...AS/400 is NOT a mainframe
I think the generally-accepted criteria for a mainfame are:
(1) multi-user with fine-grained security model
(2) multiple access mechanisms (LAN, WAN, multiplexed terminals)
(3) multiple storage layers (caches, core, paging devices, disk storage, backup media), with redundancy and partitioning
(4) high-scalability, high-throughput busses
(5) error detection and correction (ability to 'rewind' your virtual machine at least a few steps back) which typically requires CPU redundancy, very good management of CPU state, and SECDED memory
(6) multiprogramming with good handling of parallelized tasks
(7) batch execution, and automatic recovery from nearly every imaginable error condition
All of this needs to be pretty transparent to applications and users, too.
--TheOrangeSquid Is it any wonder things seem so awry? We swim in a sea of confusion and don't have to think to survive