Metacomputing Directory Service
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Transcript Metacomputing Directory Service
Metacomputing
Directory Service (MDS)
A Directory Service for Configuring
High-Performance Distributed
Computations (Fitzgerald et. al.)
Joel Thomas
Overview
Introduction
Design Considerations
Current Approaches
Design of MDS
Implementation
MDS With Globus
Future
Conclusion
Introduction
High performance distributed computing requires
selection, configuration
To make good decisions, timely, accurate information is
invaluable
Currently, have nonstandard ways to store/access the
right kind of data
The Metacomputing Directory Service (MDS) hopes to
provide a scalable service to handle this need
Design Considerations
Performance
Scalability and cost
Uniformity
Expressiveness
Extensibility
Design Considerations(cont.)
Multiple Information Sources
Dynamic data
Flexible access
Security
Deployability
Decentralized maintenance
Current Approaches
Uname, sysinfo
Simple Network Management Protocol(SNMP),
NIS(Network Information Service)
PVM(Parallel Virtual Machine), MPICH (Message Passing
Interface)
DNS (Domain Name Service)
X.500, LDAP (Lightweight Directory Access Protocol)
Chose to integrate existing systems as much as possible
But use LDAP to organize
Design of MDS
Representation and Data Access
Data Model
Implementation
Representation
Borrows straight from LDAP
Entry: instance of person, network, computer, etc.
Type is created by associating an object class
Directory Information Tree (DIT)
hierarchical, tree-structured name space
Distinguished Name (DN)
path from leaf to root entry
<hn = dark.mcs.anl.gov
ou = MCS,
o = Argonne National Laboratory,
o = Globus,
c = US
>
DIT example
Object Classes
LDAP has set of standard class definitions, which can be
extended (top, group classes, etc.)
Defines attributes for an entry, and what values those
attributes may contain
Attributes may be required or optional
Can use inheritance to build new classes
Data Model
Consists of DIT hierarchy and object class definitions
Computer centric, not network centric
People, hosts, communication networks under
organization
Data Model (cont.)
GlobusHost
GlobusNetwork
Link protocol (ATM, Ethernet)
Network topology(bus, ring)
Physical media (copper, fiber)
GlobusNetworkInterface
Physical characteristics (speed) and hardware address
Hosts contain network interfaces
Network interfaces attached to networks
Configuration example
MDS representation
Data Model (cont.)
Physical vs. Logical Network info
Single network, multiple protocol stacks
Each may have distinct interface and performance
Images: multiple logical views of the same physical
network (RFC 1609)
contains new information, and pointer back to physical
Physical has reference to all images that point to it
GlobusHostImage
GlobusNetworkImage
GlobustNetworkInterfaceImage
Implementation
While LDAP interface met most needs, default
implementation was somewhat slow
Problems:
Single information provider
Client/server architecture
Scope of Data
Allows info providers to provide information per attribute
Time to Live (TTL) for attribute (before refreshing)
Update scope: process, computation, global
Sample queries
What are the network interfaces for ATM?
Find GlobusNetworkInterface->GlobusNetwork
(link_protocol=ATM)
For that GNI, GlobusNetworkInterface>GlobusNetworkInterfaceImage (ip_address)
Which nodes can use vendor protocols on fast internal
networks?
Two GlobusHostImages belong to the same
GlobusNetworkImage object
MDS Recap
MDS with Globus
Nexus communication module
Uses MDS to find out what low-level mechanisms are between
modules
Select between mechanism, based on rules
Rules based on dynamic information or programmer preference
Code runs unchanged, but can adapt to meet performance
needs
I-WAY TestBed (heterogeneous virtual machines)
Resource Location
Resource Brokers
Future
Use in GUSTO
Extend Globus components to use MDS
Expand information sources
Optimize for common operations
Sophisticated applications (e.g. resource scheduling)
Performance metrics
Conclusion
Designed to provide dynamic information in a timely,
scalable manner
Take advantage of LDAP flexibility and growing usage in
industry
Provide information richness in extensible manner