CSCI 4534 - Operating Systems

Assignment 4 Requirements

Operating system presentation

[50 points] This is not an individual task. You are expected to join a project team comprising a total of exactly 4 students. Your joint task is to present the inner workings of an operating system:

one team will cover Windows 2000 (Mr. Dinh Lan, Mr. Doan Thanh, Mr. Do Hai, Mr. Le Tuan),
the other will cover Linux (Mr. Vu Dat, Mr. Le Nam, Mr. Nguyen Tuan, Mr. Nguyen Phuong).

Your team presentation should last at least 1:40 hours and at most 2 hours, with each student presenting for a minimum of 25 and a maximum of 30 minutes; the specific date and times are posted on the course syllabus. You are expected to cover the material at the same level of depth as it is covered in your textbook. The following is a suggested approach to a successful presentation, containing additional clarifications on expectations:

A rough understanding of the full breadth of the operating system is an essential starting point. So all team members should read chapter 20 (Linux team) or chapter 21 (Windows 2000 team).
Assign team members to specific areas of operating system functionality, such as memory management, file system, etc. Each team member should reread the portions of chapter 20 or 21 which cover their assigned area(s). Your team need not cover areas of functionality which are not part of the overall course syllabus, such as networking.
Each team member should then review the corresponding earlier chapters in the book for their topic. The textbook often presents information on a specific operating system to illustrate general concepts, e.g. Windows 2000 Threads are covered in section 5.6.
Be aware that some information on Windows 2000 is covered in the book under Windows NT (which is the general family of which Windows 2000 is a recent version). Similarly, some Linux behaviour is discussed under general UNIX behaviour (since Linux is a UNIX variant).
If the book's explanation is insufficient, consult additional resources: the book's appendix A on FreeBSD (see the course syllabus for the book's web page), on-line Linux documentation, MSDN, Microsoft Support and TechNet, newsgroups, friends, peers, etc. You may also consult members of the other team; this is not a competition.
The team performance will be assessed as a whole, and every team member will receive the same number of points for this task. So stronger team members should assist weaker ones in completing their tasks. Also, coordinate to ensure that you won't cover a topic more than once, and that your presentation is cohesive; the order of presentors is up to you.
To earn full points, you'll need to present your material with technical accuracy, sufficient depth, good visual aids and slides, using excellent English, and within the specified time limits. So, in addition to understanding the material, leave yourselves time to prepare a good presentation.
Try to make the most out of your presentation: invite friends, mentors, co-workers, old teachers, and others as you see fit. This will be a chance to show off your depth of knowledge as well as teach your peers (and your instructor). Use it as an opportunity to advertise your skills and knowledge.

Sounds tough? It is indeed. But it's also realistic. Consider the following not-at-all-hypothetical scenario:

You work for Sun Microsystems and you are about to leave for a 3-month sabbatical in Vietnam in two weeks. Even though you announced your sabbatical 6 months ago, you are just told that Sun's India team will be handling bug fixes for your code while you are gone, and you must prepare a presentation to describe it to them.
You have to describe 60,000 lines of code you wrote over 3 years, in 3 hours between 6p-9p because India wakes up around then and at most 3 hours can fit on the video archive DVD. Your presentation will be over a slow shared VNC link so you can only rely on slides (no whiteboard). Audio will travel over a low-quality voice-over-IP, so you must speak clearly and slowly; your audience speaks English as a second language and so do you, but they are Indian and you are not, so your accents are mutually incomprehensible even without the voice-over-IP compression artifacts.
Another 40,000 of code you wrote you had passed on to a coworker two months earlier, but he decided he no longer wanted to work on it last week (and changed departments within Sun). So you just found out you have to cover that material, too.
Another 20,000 of code you wrote you had passed on to a coworker for the last year, but he abruptly left Sun two weeks ago leaving no documentation on his activities or information on his whereabouts. You have to figure out what changes he made over the last year, and cover all this in your presentation, too.
Your presentation is in 5 days. Panicking and running away to Mexico is not an option unless you want your four cats to eat you alive when you can no longer afford to feed them.

Disk controller

You are given an extensible simulator of a disk controller in csci4534.controller.MainSimulator. This simulator keeps track of a set of simulated disks installed on a simulated system, as disk operations take place. All disks are managed by a single controller. For example,

control.bat SimpleController 3 4 5 50 w:0:1 w:30:2 r:0 r:30 d:0:2 r:0 d:1 r:30

simulates disk behaviour for a system with 3 initially identical disks, where each disk has 4 blocks and each block stores 5 bytes. The specified simple controller SimpleController can store a total of 3*4*5=60 bytes, as this is the total capacity of all disks combined. But we are requesting an actual capacity of 50 bytes. This controller does nothing with the remaining 10 bytes, but other controllers can use them as spares or for improved reliability. Of course, if the requested actual capacity is incompatible with the controller's management policy (e.g. if we ask this simple controller for 70 bytes), the controller reports an error during disk formatting.

In addition to the disk and controller configurations, the above command-line specifies a series of disk operations:

We first write the value 1 at byte offset 0; the byte offset is a number between 0 and 49 since we requested 50 bytes of actual capacity. Also, the byte value should be specified as an integer between -128 and 127.
We then write the value 2 at byte offset 30, followed by two read operations as offsets 0 and 30.
We then forcibly damage block 2 of disk 0, thereby rendering it inaccessible; the block index is a number between 0 and 3 since each disk has 4 blocks, and similarly the disk index is between 0 and 2 since we have 3 disks. This operation is not done via the disk controller; instead, we are corrupting the (simulated) disk without the controller's knowledge. This is a realistic scenario: the controller only discovers the damage when it tries to access the disk.
After another read at offset 0, which works fine, we wholly damage disk 1, as if its power supply had just burnt out: no block of the disk is any longer accessible. As a result, our subsequent attempt to read at offset 30, which is stored on disk 1, fails.

For the above input, here is the output we get (after making sure the simulator is first compiled via make.bat):

Controller: csci4534.controller.SimpleController
w@0=1
w@30=2
r@0=1
r@30=2
Damaging disk D0, block 2: done
r@0=1
Damaging disk D1: done
r@30=csci4534.controller.BadDiskException: Disk D1 is damaged
D0:[(1,0,0,0,0);(0,0,0,0,0);bad;(0,0,0,0,0)]
D1:bad
D2:[(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]

You are given the implementation of this simple controller in csci4534.controller.SimpleController and its helper csci4534.controller.SimpleBytePosition; in general, you can substitute SimpleController on the command-line with any other implementation of the csci4534.controller.Controller interface. Study this interface and those classes, along with the rest of the provided code, and pay particular attention to the following:

Read very carefully the fine details in the class comments of the provided class stubs (the provided partial classes you have to fully implement).
Study csci4534.controller.SpareController, which is more complex than SimpleController. Its helper csci4534.controller.StripedBytePosition is something you have to implement, so the spare controller is not fully functional even though the majority of its implementation is provided to you.
Observe that the class hierarchy for the completed simulator is already provided. The separation of controllers into csci4534.controller.ControllerBase subclasses and helpers into csci4534.controller.BytePosition subclasses should help you save time figuring out how to factor out common algorithms.
Some helper methods are also stubbed out to ease your code design and hint at the commonalities across controllers. Feel free to ignore them if they confuse you more than they help you.
For most classes, it might be convenient to read first the HTML documentation produced from the code's javadoc comments (by running jdoc.bat). The HTML documentation doesn't cover everything (e.g. it doesn't cover in-line comments or private methods), but it's more readable, esp. for sections containing math equations.

After you have finished studying the provided code, carry out the following tasks:

[5 points] Implement StripedBytePosition.

Test your implementation via the provided SpareController. Note that this controller remaps disk blocks to replace inaccessible ones with spares. So, for example, the disk operation d:0:0 may damage two different physical blocks at different points in time. And if you run

control.bat SpareController 3 4 5 30 d:0:0 w:0:1 d:0:0 w:0:1 w:0:1

you will get the output

Controller: csci4534.controller.SpareController
Damaging disk D0, block 0: done
w@0=csci4534.controller.BadBlockException: Disk D0, block 0 is damaged
Damaging disk D0, block 0: done
w@0=csci4534.controller.BadBlockException: Disk D0, block 0 is damaged
w@0=1
D0:[(1,0,0,0,0);(0,0,0,0,0);bad;bad]
D1:[(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D2:[(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]

[5 points] Implement csci4534.controller.RAID0Controller. You do not need a special helper csci4534.controller.RAID0BytePosition for this controller: use one of the other helpers. As an example of this controller's operation, the command-line:

control.bat RAID0Controller 3 4 5 30 w:0:1 w:1:2 w:5:3

should produce the following output:

Controller: csci4534.controller.RAID0Controller
w@0=1
w@1=2
w@5=3
D0:[(1,2,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D1:[(3,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D2:[(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]

[20 points] Implement csci4534.controller.ParityController and csci4534.controller.ParityBytePosition. Pay particular attention to the efficiency of parity computations. In our simulator, all computations are done in memory, but a real disk controller has to operate on data stored on disk. Because disks have much longer access times than memory, reads/writes to the simulated disks should be minimized to provide a more realistic simulation.

[4 points] Implement csci4534.controller.RAID4Controller and csci4534.controller.RAID4BytePosition. As an example of this controller's operation, the command-line:

control.bat RAID4Controller 3 4 5 40 w:0:1 w:1:2 w:5:3 w:10:4 w:15:5 w:16:6

should produce the following output:

Controller: csci4534.controller.RAID4Controller
w@0=1
w@1=2
w@5=3
w@10=4
w@15=5
w@16=6
D0:[(1,2,0,0,0);(4,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D1:[(3,0,0,0,0);(5,6,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D2:[(2,2,0,0,0);(1,6,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]

[4 points] Implement csci4534.controller.RAID5Controller and csci4534.controller.RAID5BytePosition. As an example of this controller's operation, the command-line:

control.bat RAID5Controller 3 4 5 40 w:0:1 w:1:2 w:5:3 w:10:4 w:15:5 w:16:6

should produce the following output:

Controller: csci4534.controller.RAID5Controller
w@0=1
w@1=2
w@5=3
w@10=4
w@15=5
w@16=6
D0:[(2,2,0,0,0);(4,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D1:[(1,2,0,0,0);(1,6,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D2:[(3,0,0,0,0);(5,6,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]

[10 points] Implement csci4534.controller.RAID1Controller and csci4534.controller.RAID1BytePosition but without spare disks. You are still required to implement disk mirroring since this is a key property of RAID 1.

[10 points] Add support for spare disks to csci4534.controller.RAID1Controller. Note that this controller remaps spare disks to replace damaged ones with spares. So, for example, the disk operation d:0 may damage two different disks at different points in time. And if you run

control.bat RAID1Controller 6 4 5 40 w:0:1 d:0 w:0:1 d:0 r:0

you will get the output

Controller: csci4534.controller.RAID1Controller
w@0=1
Damaging disk D0: done
w@0=1
Damaging disk D4: done
r@0=1
D5:[(1,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D1:[(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D2:[(1,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D3:[(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0);(0,0,0,0,0)]
D0:bad
D4:bad

Make sure all your code is well documented in the same simple, succinct style that the provided code is documented. As the syllabus states, points will be deducted for poorly commented code you write for this or any other programming task in this course.

[1 point] How much time did you spend on this section?

[1 point] Summarize in a concise list the key concepts and/or technologies that this assignment helped you digest. You don't have to explain the listed items; just name them.