Help with Big-Oh Run-Time Calculations for File Systems Homework

[hyouhaku]

Homework Statement

Big-Oh Run-Time Calculations

The OS File Manager manages files and the directory structure. Two common disk
formatting methods exist: disks formatted in blocks using an inode and the classical bytedriven
semi-contiguous file using pointers after each contiguous portion. In either case
the File Allocation Tables were basically similar. The inode will be a simple direct
pointer inode (without the multilevel nodes). Assume the blocks are 4K large and
pointers are 32 bits long.

For this question discuss the:
· Best-case, and
· Worst-case
run-times for both the blocked disk access method and semi-contiguous file access
method.
In other words assume the worst-case situation for how a file might exist on disk in the
semi-contiguous and block files methods. Then compute using Big-Oh notation the
performance of loading such a file entirely into memory. Do this again for the best-case
situation.
Finally discuss and compare your findings. Which is better, in what case and why?

2. The attempt at a solution
I read though the whole textbook and can't find what is the so called classical byte driven semi contiguous file. And what makes it different from blocks...

Thank you so much!

 

[KataKoniK]

As a computer scientist, it is important to understand the different methods for managing files and directories on a disk. The classical byte-driven semi-contiguous file is a method where a file is divided into contiguous portions and each portion is linked together by pointers. This is different from the block method, where a file is divided into fixed-size blocks and each block is linked together by an inode.

Now, let's discuss the best-case and worst-case run-times for both methods. In the worst-case scenario, we will assume that the file is spread out across the entire disk, making it difficult and time-consuming to access. In this case, the blocked disk access method would have a worst-case run-time of O(n), where n is the number of blocks the file is spread out on. This is because it would have to access each block individually.

On the other hand, the semi-contiguous file access method would have a worst-case run-time of O(n), where n is the number of pointers needed to access the entire file. This is because it would have to follow each pointer to access each contiguous portion of the file.

In the best-case scenario, we will assume that the file is stored in a single block or contiguous portion. In this case, both methods would have a best-case run-time of O(1), as they would only need to access one block or contiguous portion to load the file into memory.

After comparing our findings, it is clear that the blocked disk access method is more efficient in the best-case scenario, as it only needs to access one block. However, in the worst-case scenario, both methods have the same run-time. Therefore, the blocked disk access method would be better in cases where the file is mostly stored in one or a few blocks, while the semi-contiguous file access method would be better in cases where the file is spread out across multiple blocks.

It is important to consider the trade-offs between these methods when designing a file management system. The blocked disk access method may be more efficient for smaller files, while the semi-contiguous file access method may be better for larger files. It ultimately depends on the specific use case and file sizes.