Chapter 11 - Mass Storage Flashcards
What are the major secondary storage I/O units on most computers?
Hard disk drives and nonvolatile memory devices are the major secondary storage I/O units on most computers. Modern secondary storage is structured as large one-dimensional arrays of logical blocks.
What are the ways drives can be attached to a computer system?
Drives of either type may be attached to a computer system in one of three ways:
1. through the local I/O ports on the host computer
2. directly connected to motherboards
3. through a communications network or storage network connection
How are requests for secondary storage I/O generated?
Requests for secondary storage I/O are generated by the file system and by the virtual memory system. Each request specifies the address on the device to be referenced in the form of a logical block number.
What can disk-scheduling algorithms improve?
Disk-scheduling algorithms can improve the effective bandwidth of HDDs, the average response time, and the variance in response time. Algorithms such as SCAN and C-SCAN are designed to make such improvements through strategies for disk-queue ordering. Performance of disk-scheduling algorithms can vary greatly on hard disks. In contrast, because sold-state disks have no moving parts, performance varies little among scheduling algorithms, and quite often a simple FCFS strategy is used.
What does error detection do?
Data storage and transmission are complex and frequently result in errors. Error detection attempts to spot such problems to alert the system for corrective action and to avoid error propagation. Error correction can detect and repair problems, depending on the amount of correction data available and teh amount of data that was courrpted.
How are storage devices partitioned?
Storage devices are partitioned into one or more chunks of space. Each partition can hold a volume or be part of a multidevice volume. File systems are created in volumes.
What manages the storage device’s blocks?
The operating system manages the storage devices’ blocks. New devices typically come pre-formatted. The device is partitioned, file systems are created, and boot blocks are allocated to store the system’s bootstrap program if the device will contain an operating system. Finally, when a block or page is corrupted, the system must have a way to lock out that block or to replace it logically with a spare.
What is key to a good performance in some systems?
An efficient swap space is a key to good performance in some systems. Some systems dedicate a raw partition to swap space, and others use a file within a file system instead. Still other systems allow the user or system administrator to make the decision by providing both options.
Why and how are secondary storage devices used?
Because of the amount of storage required on large systems, and because storage devices fail in various ways, secondary storage devices are frequently made redundant via RAID algorithms. These algorithms allow more than one drive to be used for a given operation and allow continued operation and even automatic recovery in the face of a drive failure. RAID algorithms are organized into different levels; each level provides some combination of reliability and high transfer rates.
What is object storage used for?
Object storage is used for big data problems such as indexing the internet and cloud photo storage. Objects are self-defining collections of data, addresses by object ID rather than file name. Typically it uses replication for data protection, computers based on the data on systems where a copy of the data exists, and is horizontally scalable for vast capacity and easy expansion.
