Corporate Profile Isis Distributed Systems

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1 Corporate Profile Distributed Systems Dr. Kenneth P. Birman Founder and Chief Scientist November 21th 1995 US Govt Funded Research Project First product shipped in 1991 Acquired by Stratus Computer in December, 1993 Currently 100+ employees, 150+ customers Industries include Financial Services, Telecommunications, Manufacturing and Government/Scientific Products run on most major UNIX systems as well as Windows NT, Windows 3.1, VMS, VOS & FTX Reliable Distributed Computing What makes it hard? Required in critical applications: finance, telecommunications, air traffic control, power systems management. Traditionally addressed late in the game: first build the system, then harden it. Must be compatible with standard tools building distributed applications. Need to replicate critical data and servers, but lack tools doing this easily. Need a way to detect failures, but failure reporting is often erratic, inconsistent. Need a way to restart failed system components so they can rejoin the system, but without disrupting service. 1 Trader s Historical Trader s Historical 1 Availability historical data

1 1 Trader s Historical Trader s Historical 2 3 2 1 Availability historical data 1 Availability historical data 2 Load balancing and consistent message delivery price distribution 2 Load balancing

2 1 1 Trader s Historical Trader s Historical Availability historical data 1 Availability historical data 2 Load balancing and consistent message delivery price distribution 2 Load balancing and consisten message delivery price distribution 3 Parallel execution analytics Inconsistent failure reporting 1 A simple server Trader s Historical Availability historical data 2 Load balancing and consistent message delivery price distribution 3 Parallel execution analytics Backup Inconsistent failure reporting and primary consider one-another faulty because a reliable connection broke yet neither actually crashed Inconsistent failure reporting The problem gets even worse with more clients Backup Backup

3 Inconsistent failure reporting Who considers whom broken and why? Backup Inconsistent event reporting m 1 New requests and pricing c 0 c 1 s 0 s 1 s 2 m 0 m 2 m 3 CRASH! Service replicated availability Inconsistency causes problems... limiting application reliability! Replicated data out of sync Locks not acquired or released, or deadlock Unable to balance load or subdivide work Can't implement primary/backup fault-tolerance algorithms Can t automate system management Inconsistency is built into communication primitives in Unix, VMS, NT, Windows 95 s built on such systems must live with inconsistency: they are unreliable and hard to manage The key to is a consistency mechanism: Virtually Synchronous Process Groups Virtual Synchrony in Consistency in c 0 c 1 s 0 s 1 s 2 m 0 Built over UDP using proprietary protocols m 1 Consistent failure reporting m 3 s 3 m 4 m 2 CRASH state transfer joins Group members see events in same order State transfer provided to joining member

4 SDK turns model into "tools" Software Developer's Toolkit HOST A HOST B API group join, multicast, state transfer Replicated data and synchronization Coordinated, load-balanced request execution Fault-tolerance through software Self-management interfaces Hardware multicast big fanouts, point to point small groups Software Developer's Toolkit Software Developer's Toolkit HOST A HOST B Process Group technology HOST A HOST B Process Group technology Server processes join a group to m a service... CLIENT 1 CLIENT 2 CLIENT n Server processes join a group to m a service requests are delivered to the group with reliable group messaging Software Developer's Toolkit Product Set HOST A HOST B Process Group technology s... CLIENT 1 CLIENT 2 CLIENT n Server processes join a group to m a service requests are delivered to the group with reliable group messaging Execution can be replicated, load-balanced message and failure consistency ensures correctness of coordinated actions Core Technology

Product Set Product Set s s corba Orbix + Core Technology Core Technology Product Set Product Set s s corba corba odbc Orbix + Smalltalk Orbix + Smalltalk base Core Technology Core Technology Product

5 Product Set Product Set s s corba Orbix + Core Technology Core Technology Product Set Product Set s s corba corba odbc Orbix + Smalltalk Orbix + Smalltalk base Core Technology Core Technology Product Set RADIO: Putting It All Together s corba Orbix + Smalltalk odbc base Availability Manager Three dual 133 MHz Pentium compute nodes Three 8 gigabyte storage nodes Core Technology snmp Two network nodes mbit Enet hub or mbit Enet switch

6 Radio and Technology base Highest availability PC cluster server hosting availability technology and products. Easily serviced, hot-pluggable, self-managed. Many levels of availability: shrink-wrap NT or Unixware application benefit, if desired use active replication continuous availability. Seamlessly integrated with on your network and applications on your workstations. odbc interface databases are replicated loadbalancing; availability DB Oracle, Sybase, etc. Process Group DB Oracle, Sybase, etc. Orbix+ - The Big Picture uses single logical interface (CORBA IDL) That interface is implemented by multiple replicated objects ( object group ) Mapping of single interface to object group is provided by packaged templates logical single interface prebuilt templates physical replicated object groups Message Distribution Service Publisher Publisher Publisher MDS Server MDS Server Publishers send messages by subject Subscribers register subjects of interest MDS provides guaranteed message delivery MDS maintains persistent message streams subscribers that leave and return Subscriber Subscriber Subscriber Reliable Network File System Availability Manager A R B R Fault-tolerant infrastructure supervising applications and critical servers Simple graphical interface is easy to use Replicates files across multiple servers Removes single points of failure Automatically recovers from server failures program, server unchanged Fully customizable with rule-based scripts Sensor/action model instruments your application in natural ways that you define Automatically restarts critical servers

7 Availability Manager Event Notifications (node a) GUI (node f) Process Group of s (node b) Management Requests GUI (node g) Process Group of GUI s Action Request Node Inmation Secondary (node c) Secondary (node d) Secondary (node e) Profile of Customer s Financial Services NYSE, Swiss Stock Exchange, World Bank, Lehman Bros. data distribution, replicated databases, wide area communications, bulletin boards, management of analytics Telecommunications Northern Telecom, Southwestern Bell Intelligent switching systems and cellular services Factory Automation Advanced Micro Devices, Texas Instruments, SEMAtech Semiconductor factory automation, distributed logic simulation Government/Scientific Martin Marietta, Los Alamos Labs, Sandia Labs Command and control systems, signal processing 1. Distributed Service Node One phone number per person Trader s Historical Telephony /Digitized Voice Path x86/unix RISC/UNIX RISC/UNIX Dumb Switch Telephone Trunk Lines 2. ➀ ➁ ➂ Availability historical data Load balancing and consistent message delivery price distribution Parallel execution analytics 3. Calls, Changes, Adds, Deletes Distributed Service Node One phone number per person Distributed Service Node One phone number per person Telephony /Digitized Voice Path x86/unix RISC/UNIX RISC/UNIX 1. Dumb Switch Telephone Trunk Lines Telephony /Digitized Voice Path x86/unix RISC/UNIX RISC/UNIX Dumb Switch Telephone Trunk Lines = Ethernet 1 Replicated files digitized voice store Calls, Changes, Adds, Deletes = Ethernet 1 Replicated files digitized voice store 2 Redundancy database availability Calls, Changes, Adds, Deletes

8 Distributed Service Node One phone number per person Shop Floor Process Control Example Telephony /Digitized Voice Path x86/unix RISC/UNIX RISC/UNIX Dumb Switch Telephone Trunk Lines WorkStream Server VAX Collection Server Recipe Management Server Enet = Ethernet 1 Replicated files digitized voice store 2 Redundancy database availability 3 Load balancing call handling & routing Calls, Changes, Adds, Deletes Operator Operator PC Operator PC Operator Station Controller Station Controller Factory equipment Supported Platms Positioning Major SUN OS SOLARIS /UX IBM AIX WINDOWS NT Other WIN 3.1 ALPHA OSF/1 FTX VMS SGI PYRAMID SEQUENT Addresses application-level problems of distributed computing: Reliability Scaling Consistency Active replication versus restart-recovery availability versus server availability Vendor independent and portable Committed to integration and standards

Reliable Distributed System Approaches

Reliable Distributed System Approaches Manuel Graber Seminar of Distributed Computing WS 03/04 The Papers The Process Group Approach to Reliable Distributed Computing K. Birman; Communications of the ACM,