
P AUL A NDERSON dcspaul@inf.ed.ac.uk. Alva Couch couch@cs.tufts.edu. What is This Thing Called “System Configuration”?. Tufts University Computer Science. If we have no clear way of stating the required configuration, then we can’t create a tool to implement it!. Paul says:. Overview.
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PAULANDERSON dcspaul@inf.ed.ac.uk
Alva Couchcouch@cs.tufts.edu
TuftsUniversity
Computer Science
If we have no clear way of stating the required configuration, then we can’t create a tool to implement it!
Paul says:
OverviewHardware
Software
“Fabric” performing according to specification
Feedback (monitoring) and autonomic reconfiguration
Specifications& Policies
The configuration
problem
Paul says:
“Behaviour” or “implementation” ?
“Host-level” or “network-level” ?
“Complete” or “partial” ?
“Procedural” or “declarative” ?
Unstructured changes
Manual commands
Scripting/documentation
Perl, bash
Script management systems
Pikt, isconf
Declarative recipes for one host
Cfengine,lcfg,bcfg2,psgconf,…
Declarative recipes for a fabric
Lcfg,pan,tivoli,…
Ad-hoc: control whatever’s convenient
Incremental: control a few things
“abuse of cfengine”
Bare metal: rebuild from scratch
“deterministic”
Can repeat a build
with exact same effect
“reproducible”
Can recover from
unforeseen developments.
“convergent”
ad-hoc
federated
Cost per unit time
incremental
proscriptive
Time and Scale
Retraining
Loss of ownership
Cost per unit time
Loss of “memory”
Time and Scale
documentability
interchangeability
Cost per unit time
reproducibility
Time and Scale
federated
proscriptive
Slope is unit cost
Where are the crossings?
Lifecycle cost
ad-hoc
incremental
Time and Scale
Alva says:
Alva says:
} difference
in cost!
Lifecycle cost
Paul
Alva
Time and Scale
A → B means “cost of A drives cost of B”
planning
installation
expectations
adoption
testing
scale
maintenance
training
lifecycle
policy
troubleshooting
insurance
heterogeneity
incidents
requests
changes
downtime
threats
risks
Manual management
A → B means “cost of A drives cost of B”
planning
installation
expectations
adoption
testing
scale
maintenance
training
lifecycle
policy
troubleshooting
insurance
heterogeneity
incidents
requests
changes
downtime
threats
risks
Incremental management
A → B means “cost of A drives cost of B”
planning
installation
expectations
adoption
testing
scale
maintenance
training
lifecycle
policy
troubleshooting
insurance
heterogeneity
incidents
requests
changes
downtime
threats
risks
Proscriptive management
A → B means “cost of A drives cost of B”
planning
installation
expectations
adoption
testing
scale
maintenance
training
lifecycle
policy
troubleshooting
insurance
heterogeneity
incidents
requests
changes
downtime
threats
risks
Federated management
A → B means “cost of A drives cost of B”
planning
installation
expectations
adoption
testing
scale
maintenance
training
lifecycle
policy
troubleshooting
insurance
heterogeneity
incidents
requests
changes
downtime
threats
risks
Aspect A
Use server Y
Aspect B
Use server X
This conflict is irreconcilable without human intervention because we don’t know the intention
The user really only wants to say …
Aspect A
Use any server on my Ethernet segment
Aspect B
Use one of the servers X,Y or Z
These constraints can be satisfied to
Use server Y(assuming Y is on the right segment)
Paul says:
Aspect compositionPAULANDERSON dcspaul@inf.ed.ac.uk
Alva Couchcouch@cs.tufts.edu
TuftsUniversity
Computer Science