CST334 - Week 7

Week 7 Reflection

This week, we covered a lot about persistence, and how the OS interacts with files, directories, and I/O devices. 

I/O devices can range from memory buses to hard drives to keyboards. For a canonical I/O device, the canonical protocol is:

While (STATUS == BUSY)
; // wait until device is not busy (polling the device)
Write data to DATA register
Write command to COMMAND register
(Doing so starts the device and executes the command)
While (STATUS == BUSY)
; // wait until device is done with your request 

The basic protocol to interact with an IDE disk is:

  1. Wait for drive to be ready (polling).
  2. Write parameters to command registers.
  3. Start the I/O.
  4. Data transfer.
  5. Handle interrupts.
  6. Error handling.

I/O time, or TI/O, is calculated by the seek delay + rotational delay + transfer delay. In other words, 

TI/O = Tseek + Trotation + Ttransfer

The rate of I/O is the size of the transfer divided by the I/O time, or

Sizetransfer / TI/O

Disk scheduling is similar to job scheduling, however the length of a disk request (read: job) can be estimated by calculating the . Some disk scheduling approaches include SSTF (shortest seek time first), nearest block first (NBF), and elevator (sometimes known as SCAN or C-SCAN). To avoid resource starvation, elevator sweeps back and forth across a disk and handles requests if they haven't been serviced yet. Elevator queues requests that have already been handled behind the sweep.

Files and directories both include inode numbers, though directories use it in a pair with user-readable names first. An example would be: ("directory_name", "25").

 

Comments

Post a Comment

Popular posts from this blog

CST300 - Week 4

Week 4 has been busy! I have gotten work done a lot later than I would have liked. Part 1: Education Goals My educational goals would be to expand my knowledge about Javascript. The most tangible project to put this in practice would be to create a simple interactable website, possibly using React as a frontend. One of my ideas for a capstone project would be to create a website for a tabletop game I am developing, so the practice would be great for it.   The first step would be to learn about networking -- CST311: Intro to Computer Networking and CST336: Internet Programming would be where I hone these skills. Before these classes, I would like to create a single-task web app as a practice. It would have a starting list of about 20 items, and allow the user to arrange them into 6 specific item slots, like a digital pin board. Then, once I am in these classes, I will look back at this project and see what I can do differently or what I have learned since then.   My web develop...
Read more

CST300 - Week 2

Image
CST300 - Week 2 Part 0: The CST300 Module 2 Lectures      The Peter Diamandis presentation "The future is faster than you think" provided the insight on how fast the world is operating, but at the same time, more people are gaining an education and are enabled by the internet to achieve more. I find that the talk was a bit self-serving, in that this talk was given at Brightline Initiative in the Silicon Valley, and not given in a country that is still underserved to this day. Searching the Singularity University up on Google did not give me a good impression of their current deeds either, with embezzlement, SA, and discrimination given to me first, then my actual question after (the location of the university, in Silicon Valley).      The article "The Future of Software Engineering: Key Emerging Trends in 2024" begins as a discussion about the current downward trend of software engineer openings. Much of the future of software engineering involves AI in so...
Read more

CST300 - Week 5

Part 1:  Support and Comment on Teammates' Goals My comment on Cody's blog.   My comment on Claudia's blog. Part 2: Capstone Ideas      I've seen two projects in Week 2: DriveDiary by Christopher McMichael & Jeremiah McGrath and Out of Mana by Nathan Simpson. These two interested me as ideas for a capstone project -- a web app for a project, and a video game.     The third project I viewed was Cue Tracer by Kyle Absten, which was a database of sourced audio log files. This one stood out to me as a good project that has a much wider audience than the standard computer science audience -- in this case: videography, filmography, broadcasting, the music industry, and others. Creating a searchable database that catalogues a specific hobby's published material can also be a good idea for a capstone project.    Three possible capstone projects for me are: A web app for an in-development tabletop role-playing game written by me. Th...
Read more