Vignesh Sankaranarayanan wrote:
>The 'hour' doesn't mean anything then.. ? from the MSU
>definition (MSUs is an hourly measure (A million service
>units (MSU) >is a measurement of the amount of processing
>work a computer can perform in one hour)
Yes, it means something. I'll try again: think of MSUs as a flow *rate*, "X
tasks per hour."
I'll try another analogy. Let's suppose you own a factory, right now it has
6 employees, and each employee can make 3 shirts per hour. That's a total
of 18 shirts per hour -- "18 Made Shirt Units (MSUs) per hour." Make sense
so far?
Let's further suppose that you can add employees and increase output
linearly. So if you double the number of employees to 12, then your factory
can output 36 MSUs per hour. Or cut the number of employees to 3, and you
now have a 9 MSU factory.
OK, now the government steps in and imposes a tax based on your MSUs. The
tax is 200 rupees per MSU per month, minimum 600 (the tax on 3 MSUs). The
tax is based on the maximum number of employees in your factory during the
last month. So, for example, to calculate the tax bill for last month
(September), the government sees that you had 8 employees working on
September 2 between the hours of 10:00 a.m. and 2:00 p.m., and that was
your maximum for the month. So your factory had a peak of 24 MSUs (8
employees times 3 shirts per hour), thus they send you a bill for 4,800
rupees (24 times 200 rupees per MSU).
MSUs is a flow rate measure, that's all. That doesn't mean your factory
(mainframe) *must* run at its maximum flow rate for any length of time, or
for any time at all. But the factory (mainframe) is *capable* of running at
that maximum flow rate, given a particular number of employees ("MIPS").
Yes, you can tell your factory employees to come to work (to the factory)
and stay on duty, but not to sew any shirts. If the total staffing on shift
is 10 employees, for example, then you have a 30 MSU factory in this
example. But whether those 30 MSUs of factory *capacity* are producing
useful output or not is a separate question. Or you could tell those 10
employees to sew 1 shirt per hour, even though they are capable of 3 shirts
per hour -- you can make the 30 MSU factory run at 10 MSUs. Or you can tell
the employees to sew 1 shirt during the first 20 minutes of each/every hour
and then to take a 40 minute coffee break for the remainder of each/every
hour. So for the first 20 minutes of each/every hour the factory runs at 30
MSUs, and then for the last 40 minutes of each/every hour the factory runs
at 0 MSUs (but is capable of running at 30 MSUs). That's possible, too. Or
you can tell those 10 employees to trade turns at one sewing machine in the
factory, in 6 minute shifts. If you do that, then that's just like having 1
full-time employee (assuming no switching overhead), and so you get 3 MSUs
of output (3 Made Shirt Units per hour).
Does all this make sense yet? The concept of a maximum flow rate (whether
utilized or not, at any particular moment in time) seems pretty simple to
me, but maybe I'm not explaining it well if it's still confusing.
--------------------------------------------------------------------------------------------------------
Timothy Sipples
IT Architect Executive, Industry Solutions, IBM z Systems, AP/GCG/MEA
E-Mail: [email protected]
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