Mark C. Ballew wrote:
This question might be targeted more toward James, but what do people
think about Linux on the Mainframe for deploying Linux? I'm looking
at using zSeries machines to run various databases under Linux, since
mainframes are often acclaimed for their i/o abilities.
Assuming money is no problem, what would be the reasoning behind
going for a normal Linux server setup with fail over compared to
using an underlying operating system such as zOS? What about a Linux
server set up running UML or Xen versus zOS?
Factors that I can think of off hand is that adding more Linux
servers is easier, and software compiled for i386/x86-64 would be far
more common, but for the software I plan to run, a zOS port would
certainly be available. Other things would be the physical labor
involved: that is something that will always be limited. There are
probably more people in the industry that know how to manage Linux
servers than Linux on zOS. zOS is also a "blackbox", so an admin
would have to rely on the vendor instead of training to fix a problem
in some cases.
Any one else have thoughts?
Do you have the zSeries available already?
Last I recall, they were pretty darn expensive on kind of a
per-horsepower basis... if you can segment your applications into sets
which will each perform well on a single x86 box, you can probably save
a lot of money and have simpler upgrade paths.
If you need to be able to scale an application... the mainframe side
does pretty well with their 'lpar's for 'vpar's, or whatever the heck
they're calling it these days.
However.. yer still going to see a performance limit on linux/SMP on the
mainframe side, as you scale over 4 processors, if you're doing heavy
I/O because last I checked, linux still didn't do much in the way of
fine grained locking - hence a lot of processes competing for the same
I/O which, on an HPUX or Sun box would not have to wait for such a big
lock. (Unless IBM has a better kernel which fixes that).
But a lot of applications wont need that scalability.
I think the big question is whether your applications will need to
scale.. and how high they'll need to scale.. that should tell you
whether you can go with the lower priced x86 boxes over a mainframe.
There are also tricks you can use under Oracle (if that's yer database
backend), to scale I/O pretty linearly with processors using raw
devices... not certain about other databases.
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