Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
UNIX systems utilized to use disk-layout optimizations based on the rotation position of disk data however modern implementations including Linux simply optimize for sequential data access. Why do they do therefore? Of what hardware kind does sequential access take advantage? Why is rotational optimization no longer consequently useful?
Answer: The performance quality of disk hardware have changed substantially in recent years. In particular numerous enhancements have been introduced to raise the maximum bandwidth that can be achieved on a disk. In a modern system there is able to be a long pipeline among the operating system and the disk's read-write head. A disk I/O demand has to pass through the computer's local disk controller over bus logic to the disk drive itself as well as then internally to the disk where there is probable to be a complex controller that can cache data accesses as well as potentially optimize the order of I/O requests.
For the reason that of this complexity the time taken for one I/O request to be acknowledged and for the next request to be generated and received by the disk can far exceed the amount of time between one disk sector passing under the read-write head as well as the next sector header arriving.
In order to be able efficiently to read multiple sectors at once, disks will employ a read ahead cache. While one sector is being passed back to the host computer the disk will be busy reading the next sectors in anticipation of a request to read them. If read needs start arriving in an order that breaks this read ahead pipeline performance will drop.
Accordingly performance benefits substantially if the operating system tries to keep I/O requests in strict sequential order. A subsequent feature of modern disks is that their geometry can be extremely complex. The number of sectors per cylinder is able to vary according to the position of the cylinder- more data can be squeeze into the longer tracks nearer the edge of the disk than at the canter of the disk. For an OS (operating system) to optimize the rotational position of data on such disks it would have to have complete understanding of this geometry as well as the timing characteristics of the disk and its controller. In general, only the disk's internal logic can determine the optimal scheduling of I/Os and the disk's geometry is probable to defeat any attempt by the operating system to perform rotational optimizations.
what are the factors influencing the choice of a mode of transportation?
What is paging? Name the different paging techniques. Paging is a memory management method that permits the physical-address space of a process to be noncontiguous. Paging evad
What is the use of fork and exec system calls? Fork is a system call by which a latest process is created. Exec is also a system call, which is used after a fork by one of the
File System Interface and Implementation The Nachos file system, as distributed, uses a single-level index allocation method for data allocation of files. In the current design,
Question: Concurrency and Synchronization a) Define the following terms: I. Critical section II. Mutual Exclusion III. Deadlock IV. Starvation. b) Name three methods w
Question: (a) Answer the following questions based on the code snippet below. 1. int main (int argc, char *argv[]) 2. { 3. 4. pid_t processId; 5. 6. processId =
KERNEL-LEVEL THREADS (KLT) In this level every thread management is done by kernel .No thread library except an API system calls to the kernel thread facility exists. The kern
What is the basic approach of page replacement? If no frame is free is available, find one that is not presently being used and free it. A frame can be freed by writing its con
Explain about file allocation methods? The main problem in direct-access nature is how to assign space to these files so that disk space if utilized effectively and files can b
Q. What are the three main activities of an operating system in regard to memory management? Answer: a. Keep follows of which parts of memory are currently being used and
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +91-977-207-8620
Phone: +91-977-207-8620
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd