Subject: [eman] Energy management use cases in the EMAN applicability statement

From: Benoit Claise <[email-masked]>
Date: Tue, 30 Apr 2013 16:58:04 +0200

Dear all,

While reviewing the EMAN requirements draft, both Stephen and Sean came 
up with the same remark:

    section 3.2 - not all energy management is about simply using less,
    in the case of power harvesting devices, one may need to
    preserve energy so that it can be used when communications are
    needed (with radios being the most expensive power consumers)

Here is the change that will be done in the next version of the 
requirements draft.

OLD:

        3.2. Saving Energy Versus Maintaining Service Level

        While the general objective of Energy Management is quite clear, the
        way to attain that goal is often difficult.  In many cases there is
        no way of reducing power without the consequence of a potential
        service (performance or capacity) degradation.  In this case, a
        trade-off needs to be made between service level objectives and
        energy minimization.  In other cases a reduction of power can easily
        be achieved while still maintaining sufficient service level
        performance, for example, by switching entities to lower Power
        States when higher performance is not needed.

NEW:

        3.2. Saving Energy Versus Maintaining Service Level

        One of the objectives of Energy Management is to reduce the
        Energy consumption. While this objective is clear, the
        way to attain that goal is often difficult.
        In many cases there is
        no way of reducing power without the consequence of a potential
        service (performance or capacity) degradation.  In this case, a
        trade-off needs to be made between service level objectives and
        energy minimization.  In other cases a reduction of power can easily
        be achieved while still maintaining sufficient service level
        performance, for example, by switching entities to lower Power
        States when higher performance is not needed.

However, there is an extra action item for the applicability statement 
authors: they should include the different Energy Management use cases.
For example, Sean mentioned:

    Is energy management all about actually using less energy?  I
    would have thought energy management was about informing the management
    entity about the power consumption to allow them to take some action,
    which just as well might be no action because it's operating in some
    normal range.  I mean I can run a nuclear reactor right at the minimum
    Level of Energy needed or maybe I can be somewhere above that minimum in
    a safety zone.  Then again, maybe minimal is the lower bar of the safety
    bar.  Regardless, I'm sticking with my first sentence ;)

Regards, Benoit