Holistic Quota Management Michael Gilfix [email protected] November 6 th, 2002 LISA 2002.
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Transcript of Holistic Quota Management Michael Gilfix [email protected] November 6 th, 2002 LISA 2002.
Why Quotas? Users expect guaranteed access to
resources Finite resources Ensures that users “play nice”
Well understood paradigm “Gets the job done” Widely applicable to resource management:
Disk Space Bandwidth Quality of Service
Traditional Systems
Individuals assigned usage limits Soft Limits vs. Hard Limits Groups as a solution to mass management
Limited facilities for analysis Manipulation limited to user-level or group-level No easy way to determine efficiency of current
quota policies No easy way of working with the “bigger picture”
“Bigger Picture” is Key
Some vital questions: How much am I promising compared to how
much I have available? How effective are, or how much is wasted by, my
current policies? How much “headroom” do I have to work with? Who needs less and who needs more?
All difficult to answer without global analysis
In Search of Inspiration
Resource management as a scheduling problem Dynamic resource management based on
“competitive counterforce” A control-theoretic model
Value of the whole is greater than the sum of its parts
Fusion
“Competitive Counterforce”: Emphasize relative share Increase for one means less for others
The control-theoretic model: Operating curves as an effective means of
defining system behavior Encourages a much more dynamic system
Value of the whole: Suggests a “fuzzy” visual interface
Towards a New Model Resource is treated as finite and continuous Each user is given a fraction of that resource System Administrator defines a distribution curve to
define the resource sharing policy Area constrained to one-to-one correlation with total
amount of resource Distribution curve is divided into slices whose widths
are proportional to the number of users of the resource
Users are either assigned or compete for a slice Operations are global: Giving more to one takes
from everyone else
The New Model Illustrated
The New Model IllustratedA Current Quota Implementation
in the New Model
Benefits
Separation of policy from implementation Closer to a service model Makes policy easier to understand
Encourages informed changes to individual limits Changes for individuals do not compromise the
general policy Puts perspective on over-subscription:
User shares decrease as user-base increases Allows for a stronger service guarantee
Scales “automatically” as underlying resource amount changes
Creating a Proof-of-Concept
A meta-management approach Biggest concern is adoption for POC Must be able to interoperate with existing
quota systems Implementation is a compromise between
model and inter-operability Implementation is consistent in interface Interface focuses on the “global picture”
Faithful Visualization
Chaining step functions as an accurate and scalable depiction
Avoids visual artifacts
A Plot at Full View A Zoomed Sub-Section
Exposing trends
Hierarchical sorting as a powerful tool for trend analysis Exposes categories of users, or service levels
automatically Exposes trends within population categories User groupings presented reflect reality Renders displays with meaningful distributions
Some Interesting Conclusions
The new model helps answer the “bigger picture” questions: Over-Subscription Effectiveness Working room User need satisfaction
Enables global operations Pareto distribution may play an important role
in modeling file size distributions in networks
Where to now?
Evaluation of the proof of concept Building a full implementation
Implementation of the privilege mechanism will eliminate many inherent problems in the POC
Direct support for explicit over-subscription Applying the Qualm concepts to other areas
of resource management Experimenting with dynamic schemes using
this framework
Qualm is freely available at:http://qualm.sourceforge.net
Orhttp://www.sourceforge.net/projects/qualm
Contact Information
Michael GilfixTufts University
This talk was sponsored by: