What is SSTF scheduling in disk scheduling?
SSTF is abbreviation of Shortest Seek Time First (SSTF) which is a disk scheduling algorithm. It selects the request which is closest to the current head position before moving the head away to service other requests. This is done by selecting the request which has the least seek time from the current head position.
Which disk scheduling algorithm is the most suitable for solid state drives Why?
10.10 Explain why SSDs often use an FCFS disk-scheduling algorithm. Because SSDs do not have moving parts and therefore performanceis insensitive to issues such as seek time and rotational latency. Therefore, a simple FCFS policy will suffice.
What is a disadvantage of the SSTF scheduling algorithm?
In SSTF there is an overhead of finding out the closest request. Starvation may occur for requests far from head. In SSTF high variance is present in response time and waiting time. Frequent switching of the Head’s direction slows the algorithm.
Is disk scheduling useful in a single user environment?
Yes, disk scheduling other than FCFS scheduling can be useful in a single-user environment. SSTF is useful when the data sets are near each other.
Which disk scheduling is best?
With the classical approach of disk scheduling algorithm, few algorithms like SSTF and LOOK will be the most efficient algorithm compared to FCFS, SCAN, C-SCAN and C- LOOK disk scheduling algorithm with respect to these parameters.
What is the main goal of disk scheduling algorithm?
the most widely known algorithm for scheduling the request is SSTF or LOOK algorithm. the main goal of this and most of other disk scheduling algorithm is to reduce the number of disk head movement thereby reducing the seek time. To achieve this, we should have a fast access time and large disk bandwidth.
Why is disk scheduling important?
Disk scheduling is also known as I/O scheduling. Disk scheduling is important because: Multiple I/O requests may arrive by different processes and only one I/O request can be served at a time by the disk controller. Thus other I/O requests need to wait in the waiting queue and need to be scheduled.
Why rotational latency is usually not considered in disk scheduling?
Most disk scheduling only use seek time. Most disk scheduling do not consider rotational frequency because in most modern system, the actual physical location of blocks in not available.
What is the advantage with SSTF?
Advantages- It reduces the total seek time as compared to FCFS. It provides increased throughput. It provides less average response time and waiting time.
What is SSTF program?
Shortest seek time first (SSTF) algorithm selects the disk I/O request which requires the least disk arm movement from its current position regardless of the direction. It reduces the total seek time as compared to FCFS. It allows the head to move to the closest track in the service queue.
Which kind of disk request scheduler is best suited for solid state drives *?
Noop scheduler performs best out of other traditional schedulers for SSD devices since it does very minimal operations but the read/write requests can be merged in a way which causes more writes to SSD.
Why do stable storage devices often use FCFS disk scheduling algorithm?
Answer: ssds do not have any rotating disk or any moveable part which makes the ssds to use the algorithm of fcfs (first come first serve). Step-by-step explanation: As they do not contain any moving part so the performance of ssds are insensitive.
Why SSTF scheduling is more efficient than FCFS?
In the elevator scheduling, we saw that the effects are optimal because it is more efficient than FCFS but unlike SSTF, there are no starvation. Explain why SSTF scheduling tends to favor middle cylinders over the innermost and outermost cylinders. The center of the disk is the location having the smallest average distance to all other tracks.
How does the SSTF algorithm work?
* SSTF (Cont.) * SCAN The disk arm starts at one end of the disk, and moves toward the other end, servicing requests until it gets to the other end of the disk, where the head movement is reversed and servicing continues. Sometimes called the elevator algorithm. Illustration shows total head movement of 208 cylinders.
Is disk scheduling other than FCFS useful in a single-user environment?
Yes, disk scheduling other than FCFS scheduling can be useful in a single-user environment. SSTF is useful when the data sets are near each other. In the elevator scheduling, we saw that the effects are optimal because it is more efficient than FCFS but unlike SSTF, there are no starvation.