Tracy R Reed wrote:
I would definitely like to learn more about mainframes and apply the
good ideas from the mainframe world to the Unix world. I understand that
mainframe hardware is of the highest quality and fault tolerant with
lots of emphasis put on IO and I hope we can carry more of that over
into the Unix/PC world. I am still trying to understand what advantages
the mainframe software world has. My biggest complaint (which I recently
voiced on slashdot) is that we have no way of learning about mainframes.
The average person can't afford one. The average (small) company can't
even afford one! And Wade is only the second person I have ever met in
my life who had any real experience with mainframes. I think mainframes
would be a lot more widespread if IBM had given the software away for
free and some minimal hardware platform on which to run it so that more
people could have access to understand the technology. I know I will
never recommend a mainframe solution to my employer until I really have
some practical experience with one. And given the amount of OLTP and
OLAP that we do around here we could probably use some of those
capabilities of a mainframe.
IBMs Power5 systems have most of the hardware benefits of the
mainframes, but run Linux and AIX, and IOS. I work with a lot of these,
and they are a great platform. You can get your hands on Power4, which
starts to do this for very little money on the used market.
What do you mean by "scheduling batch jobs"? I understand that "batch
jobs" are a major part of the workload for mainframes but I have no idea
what they really are. Would a batch job just be the generation of a
report or something? If so we schedule batch jobs out of cron and it
works just fine. Maybe the mainframes have a better way of doing it but
the way we are doing it is "good enough". I would like to be able to
allocate resources to specific tasks on the fly but I think we are
getting there with clustering and Xen. Detailed transaction logging is a
part of our application. Is it part of the OS in the mainframe world? If
so, why should the OS need to be aware of Alice buying a toothbrush?
The mainframes have workload management. This is something that you get
on all IBM platforms. They also give you means to measure, and bill for
resource usage. The batch processing is both a scheduler and a queue,
where cron is just a scheduler. Being a queue, you can ensure that
things complete quickly, but it is harder to ensure things run at
exactly the right time.
If you run Linux on a mainframe don't you lose the batch processing and
other niceties that the mainframe OS provides you? Then what you have is
a very reliable Linux box on very expensive hardware. Still better than
running it on a PC, I'm sure.
Not completely. Our Linux configuration runs withing VM, a specialized
virtualization environment that VMWARE, XEN, and others are trying to
copy. These things can run in layers. You can have the following
1 MVS->VM->Linux
2 VM->Linux
3 Linux
In the first option, you have all the functions of MVS, and how it can
interact with VM, and all the functions of VM, and how it can interact
with Linux. You also can use network protocols and VSwitch to
communicate client server style without leaving the system.
In the second option, you get all the functions of VM, and how it can
interact with Linux. This is mostly basic hardware virtualization
operations.
In the third, you have a giant, and probably wasted Linux box. You can
only run one on the entire system.
We use the first option, and still run a lot of mainframe applications
along side the Linux VM environment. 85% or more of the
http://www.usda.gov web portal is run off of this platform, along with
other sites.
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