1. Comparison of Distributed Operating Systems

2. Systems Discussed ◦Plan 9 ◦AgentOS ◦Clouds ◦E1 ◦MOSIX

3. Plan9 - 1 History ◦Bell Labs 1984 – 2002 (and on) ◦“Plan 9 from Bell Labs” based on “Plan 9 from Outer Space.” ◦Replaced Unix as primary research platform. ◦Based on 9P protocol.  Accesses all resources, local and remote.

4. Plan9 - 2 Notable architecture: ◦All system interfaces through file system. (pre- Linux) Workstation - independent working environment “Workstation” – aggregated resources, remote and local.

5. Plan9 - 3 /proc ◦All processes are visible as files /net ◦All network traffic read/written through file system Can import posix apps, emulate Berkeley socket interface through APE (ANSI/POSIX Environment)

6. AgentOS - 1 Originally designed by Harry Chen at UC, Irvine (1998) Subsumed by The Bio- Networking Architecture project ◦Grants from NSF, DARPA, and AFOSR (Air Force Office of Scientific Research)

7. AgentOS - 2 Goal: Ubiquitous Access ◦Nomadic and mobile users Based on Java VM Agent based vs. RPC ◦Adaptive vs. dummy communication Byte code inefficiency ◦Just In Time Compilers with caching

8. Clouds - 1 History ◦Clouds is actually 2 separate operating systems  Clouds V1, based on VAX kernel 1986  Clouds V2, based on Ra kernel ~1989 Purpose ◦Support distributed research at Georgia Institute of Technology

9. Clouds - 2 Clouds based on the object/thread paradigm At OS level there is only one type of object, clouds Ra kernel implements persistent virtual memory ◦Threads travel through objects ◦Entry points

10. Clouds - 3

11. E1 E1 first distributed commercially in 2005. Very much like clouds ◦Object/thread paradigm ◦Difference: Threads outside of objects Objects replicated and synchronized ◦Redundancy vs. loss of efficiency in replication

12. MOSIX - 1 Version 0 (1977) – research project on process migration ◦based on Unix 6 ◦tested on PDP 11/45 and diskless 11/10 connected by parallel I/O ◦Named: UNIX with satellite processors. Current Version, 10 (2006) [MOSIX2] ◦Supporting Linux Kernel 2.6 Generic Solution – dynamic management of resources.

13. MOSIX - 2 Core – ◦adaptive sharing algorithms ◦Preemptive process migration ◦Load balancing  Process placement  System structure Compatibility: ◦Connect with any Linux, only one MOSIX hub required

14. MOSIX - 3 Cluster – collection of computers Grid – collection of clusters Partition ◦Limited to 256 nodes (by IP addressing) Highly secure Infinitely scalable

15. Impact on Current Systems Impact on current systems ◦Plan9 file system in Linux ◦Clouds RPC model in later UNIX and windows ◦AgentOS theory behind Google Docs