1. Clustering Technology For Fault Tolerance
Jim Gray
Microsoft Research

2. What is Wolfpack?
A consortium of 60 HW & SW vendors (everybody who is anybody)
A set of APIs for clustering and fault tolerance
An enhancement to NT™ Server (in beta test )
Key concepts
System: a particular node
Cluster: a collection of systems working together
resource: a hardware or software module
resource dependency: one resource needs another
resource group: fails over as a unit: dependencies do not cross group boundaries

3. What Wolfpack Supports in V1
two node failover (twin-tail SCSI)
Apps:
File, Print, web server, IP address, Net Name
Most of Microsoft BackOffice (SQL, Exchange, Viper, Falcon,…)
Oracle
SAP
many others
Easy to program, operate, use

4. Cluster Advantages Clients and Servers made from the same stuff.
Inexpensive: Built with commodity components
Fault tolerance:
Spare modules mask failures
Modular growth
grow by adding small modules
Parallel data search
use multiple processors and disks

5. What Happens When a Component Fails?
Redundant disk or path: configure around it.
Non-redundant software: restart.
Non-redundant hardware: migrate software to surviving nodes.
Fault detection: 1 ms to 10 sec.
Failover .1 sec to 1 min.
This is standard in Tandem, Teradata, VMScluster