CST334.7 Module Seven

  

CST334.7 Module Seven

What I learned this week:

    This week we covered the topic of I/O Devices, in particular hard disks, it's primary components, both physical and digital. Physically a drive is typically composed of a platter which persistently stores data, a spindle which rotates the platter, and a disk head(attached to an arm) which is used to read and write from the surface of a platter. TDigitally, he disk is divided into sectors, composed of blocks. There are important measurements to consider when evaluating performance of a disk: rotational delay, seek time and transfer time, are summed together in order to calculate the time of I/O. Disk also have designated schedulers, and vary in approaches to managing the order of which I/O requests are file.

    We also covered RAID's which stands for Redundant Arrays of Inexpensive Disks, and are typically used in order to incorporate a faster, bigger and more reliable disk system. In order to understand the way RAID's work, consider an array of disks being tasked to work together, they re-address themselves and distribute their address space, to be evenly spread across all disks within the array. This ensures that persistence and reliability are at utmost, because if a disk fails, if you consider the type of RAID used, you could recover once lost data. When we consider types, there are several different ones, which each come with varying issues, its important to consider the use case of user before choosing. Consider you just want a copy, RAID-1 might be a good option, because at minimum a single disk can fail, yet you're capable of reading it's mirrored copy.

    Another topic we covered were file systems and their use when it comes to working with files and directories. Typically structured in a way in which important metadata is reserved at the beginning of disk space, it also contains two tables in which one points to an iNode table, and the other points to a data table(where information is stored).