Crashes and Recovery
Exams back at the end of class
Project 2, part 1 grades
Transactions and distributed transactions
The ACID properties
Isolation with 2-phase locking
Needed an at
Virtual Machine Monitors
Virtual Machine Monitors (VMMs) are everywhere
Software: VMware, Xen, Microsoft Virtual PC
Hardware: Intel VT, AMD-V
CSE 120: Principles of Operating Systems
Alex C. Snoeren
You know VMs.
(and bears, oh my!)
You used one for project 2!
History: IBM sold big mainframe computers; companies would
buy one; wanted to run apps designed for different OSes.
When you can only afford one computer.
Add a level of
Time and synchronization
(Theres never enough time)
Time in distributed systems
A baseball example
Synchronizing real clocks
The Berkeley Algorithm
Network Time Protocol (NTP)
Lamport logical clocks
quine = 'quine = %r\r\nprint quine % quine'
Security, part 1
print quine % quine
A quine is a self-reproducing program.
What does this have to do with security?
It lets you write a self-propagating
trojan horse compiler
Ken Thompsons compiler hack
From last time.
Shared key crypto with key KAB:
Intuition: Hash them together
HMAC(KAB, m) = H( (K.) | H(K . | m)
Public key crypto with KA, K-1A:
Intuition: signing is en
Guest Lecture for 15-440
Disk Array Data Organizations
October 2010, Greg Ganger
Plan for today
Why have multiple disks?
problem and approaches
Storage capacity, performance capacity, reliability
Millions of clients ! server and network
Scaling: Create system whose capacity grows with # of
clients - automatically!
This aspect attractive for corporate/datacenter ne
15-440 Distributed Systems
October 12, 2010
Please write your name and Andrew ID above before starting this exam.
This exam has 10 pages, including this title page. Please conrm that all pages are present.
This exam has a total
A Classic Problem - Dining Philosophers The Dining Philosophers problem is a classic OS problem thats usuallu stated in very non-OS terms: There are N philosphers sitting around a circular table eating spaghetti and discussing philosphy. The problem is th
15-441 Lecture 7
(Extra credit, remind me at end)
Copyright Seth Goldstein, 2008
Based on slides from previous 441 lectures
What is DNS?
How resolve name
Distributed Mutual Exclusion
Synchronizing real, distributed clocks
Logical time and concurrency
Lamport clocks and total-order Lamport
Goals of distributed mutual exclusion
Much like regular mutual exclusion
Transactions and Distributed
1) Exam Thursday
2) Exam review session
3) Homework 1 back
4) dga,vrv out until Thursday
Last time: RAID
Trade capacity for reliability
Throughput growingdelay not
The Byzantine Generals Problem
Leslie Lamport, Robert Shostak, and Marshall Pease
ACM TOPLAS 1982
Practical Byzantine Fault Tolerance
Miguel Castro and Barbara Liskov
1: of, relating to, or characteristic o
CMU 15-440: Distributed Systems
Questions about Paxos / distributed
If you havent picked up your exam yet, its
with my admin (see web page)
Even your laptop, if your parents bough
Howd we get here?
Failures & single systems; fault tolerance techniques
added redundancy (ECC memory, RAID, etc.)
Conceptually, ECC & RAID both put a master in
front of the redundancy to mask it from clients -ECC handled by memory controller,