Operations Systems C7 Flashcards
Differentiate between dedicated, shared, and virtual devices, providing examples for each category.
Dedicated devices are assigned to one job at a time, such as tape drives or printers. Shared devices, like direct access storage devices (DASD), are utilized by multiple processes simultaneously with controlled interleaving. Virtual devices, such as printers converted from dedicated to shared using spooling, combine aspects of both dedicated and shared devices.
Explain the role of I/O traffic controllers in managing devices in a computer system.
I/O traffic controllers monitor the status of devices, control units, and channels, determining available paths and managing device connections. They maintain databases containing each unit’s status and connections.
Compare the functions of I/O schedulers and process schedulers in a computer system.
I/O schedulers allocate devices, control units, and channels, prioritizing requests based on criteria like request urgency. Process schedulers, on the other hand, manage the execution of processes, determining which process to run next based on scheduling algorithms.
Discuss the responsibilities of I/O device handlers in the context of managing I/O requests.
I/O device handlers handle actual data transfer, process device interrupts, manage error conditions, and implement scheduling algorithms specific to each device type. They are responsible for the low-level management and operation of I/O devices.
How does spooling contribute to the concept of virtual devices?
Spooling converts dedicated devices into shared devices by queuing and buffering input/output data, allowing for more efficient utilization of resources and enhancing system performance.
Describe the role of the local operating system in accessing remote I/O devices in cloud computing.
he local operating system’s role in accessing remote I/O devices is similar to accessing local devices. However, cloud computing expands accessibility by providing access to a broader range of devices remotely.
Explain the characteristics of magnetic tape as a sequential access storage medium.
Magnetic tape stores records serially, with record length determined by the application program. Accessing records on tape is time-consuming, and tape density, determined by the number of characters recorded per inch, impacts storage capacity and access speed.
What is blocking in the context of magnetic tape storage, and what are its advantages and disadvantages?
Blocking groups records into blocks, improving efficiency by reducing the number of I/O operations and wasted tape space. However, blocking introduces overhead and requires software routines for management, potentially wasting buffer space when only one logical record is needed.
Discuss the efficiency of magnetic tape storage for routine secondary storage tasks.
Magnetic tape storage is inefficient for routine secondary storage tasks due to its sequential access nature, which requires time-consuming tape rotations to access records. It is best suited for files with very high (90 to 100 percent) sequential activity.
How does tape density impact the storage capacity and access speed of magnetic tape?
Tape density, determined by the number of characters recorded per inch, directly impacts the storage capacity and access speed of magnetic tape. Higher tape density allows for more data to be stored in the same length of tape, increasing storage capacity and potentially improving access speed.
What are Direct Access Storage Devices (DASDs), and how do they provide random access storage?
DASDs allow direct reading or writing to specific disk areas, offering random access storage capabilities. They include magnetic disks, optical discs, and solid-state (flash) memory.
Describe the components and organization of magnetic disk storage.
Magnetic disks typically consist of two recording surfaces formatted into concentric tracks, with each track numbered from 0 on the outer edge to the highest track number in the center.
What factors contribute to file access time on magnetic disks?
File access time on magnetic disks is influenced by seek time (the time to position the read/write head), search time, rotational delay (time to rotate until the desired record is under the read/write head), and transfer time (the time to transfer data).
Discuss the various device handler seek strategies used to minimize seek time on DASDs.
Device handler seek strategies include FCFS, SSTF, SCAN, LOOK, N-Step SCAN, C-SCAN, and C-LOOK. Each strategy aims to minimize seek time by optimizing arm movement and response time variance.
Compare the advantages and disadvantages of FCFS, SSTF, and SCAN seek strategies.
FCFS offers simplicity but can lead to extreme arm movement and longer service times under high loads.
SSTF minimizes overall seek time by prioritizing requests closest to the currently serviced track.
**SCAN **eliminates indefinite postponement but may lead to localization problems under heavy loads.
Choosing the best strategy depends on the workload characteristics and desired performance metrics.
