1. Monitoring and Fault Tolerance
Helge Meinhard / CERN-IT
OpenLab workshop
08 July 2003

2. Monitoring and Fault Tolerance: Context
Node
Configuration
System
Monitoring
Installation
Fault Mgmt

3. History (1)
In the 1990s, “massive” deployments of Unix boxes required automated monitoring of system state
Answer: SURE
Pure exception/alarm system
No archiving of values, hence not useful for performance monitoring
Not scalable to O(1000) nodes

4. History (2)
PEM project at CERN (1999/2000) took fresh look at fabric mgmt, in particular monitoring
PEM tool survey: Commercial tools found not flexible enough and too expensive; free solutions not appropriate
Architecture, design and implementation from scratch

5. History (3)
: European DataGrid project with work package on Fabric Management
Subtasks: configuration, installation, monitoring, fault tolerance, resource management, gridification
Profited from PEM work, developed ideas further

6. History (4)
In 2001, some doubts about ‘do-it-all-ourselves’ approach of EDG WP4
Parallel to EDG WP4, project launched to investigate whether commercial SCADA system could be used
Architecture deliberately kept similar to WP4

7. Monitoring and FT architecture (1)
Monitoring: Captures non-intrusively actual state of a system (supposed not to change its state)
Fault Tolerance: Reads and correlates data from monitoring system, triggers corrective actions (state-changing)

8. Monitoring and FT architecture (2)
Sensor
Monitoring Sensor Agent (MSA)
MR – Monitoring Repository
WP4: MR code with lower layer as flat file archive, or using Oracle
CCS: PVSS system
Sensor
Sensor
Local consumers
Local consumers
Local cache
A P I
Local consumers
A P I DB

9. Monitoring and FT architecture (3)
MSA controls communication with Monitoring Repository, configures sensors, requests samples, listens to sensors
Sensors send metrics on request or spontaneously to MSA
Communication MSA – MR: UDP or TCP based

10. Monitoring and FT architecture (4)
FT system subscribing to metrics from monitoring subsystem
Rule-based correlation engine takes decisions on firing actuators
Actuators controlled by Actuator Agent, all actions logged by monitoring system

11. Deployment (1)
End 2001: Put early versions of MSA and sensors on big clusters (~800 Linux machines), sending data (~100 metrics per machine, 1/min…1/day) to a PVSS-based repository
At the same time, ~300 machines started sending performance metrics into flat file WP4 repository

12. Deployment (2)
Sensors more refined over time (metrics added according to operational needs)
Both exception and performance oriented sensors now deployed in parallel (some 150 metrics per node)
More special machines added, currently ~1500 machines being monitored
Test in May 2003: some 500 metric changes per second into the repository (~150 changes/s after “smoothing”)

13. Deployment (3) Repository requirements:
Repository API implementation
Oracle based
fully functional alarm display for operators
Currently using both an Oracle-MR based repository, and a PVSS based one
Operators using PVSS based alarm screen as alternative to Sure display

14. Deployment (4)
Interfaces: C API available, simple command line interface by end July, prototype Web access to time series of a metric available
Fault tolerance: Just starting to look at WP4 prototype
Configuration of monitoring: ad-hoc, to be migrated to CDB

15. Outlook Near term: Production services for LCG-1
Add more machines (e.g. network), metrics
Software and service monitoring
Medium term (end 2003): Monitoring for Solaris and Windows, …
2004 or 2005: Review of chosen solution for monitoring and FT
Some of 1999 arguments no longer valid
Will look at commercial and freeware solutions

16. Machine control
High level: interplay of State Management System, Configuration Management, Monitoring, Fault Tolerance, …
Low level:
Past: CPU boxes didn’t have anything (5 rolling tables with monitors and keyboards per 500…1000 machines), disk and tape servers with analog KVM switches
Future: Have investigated various options, benefit/cost analysis. Will go to serial consoles on all machines, 1 head node per 50…100 machines with serial multiplexers