)A portion of RAM used to speed up access to data on a disk. The RAM can be part of the disk drive itself (sometimes called a hard disk cache or buffer) or it can be general-purpose RAM in the computer that is reserved for use by the disk drive (sometimes called a soft disk cache). Hard disk cachesare more effective, but they are also much more expensive, and therefore smaller. Nearly all modern disk drives include a small amount of internal cache.
A soft disk cache works by storing the most recently accessed data in the RAM cache. When a program needs to access new data, the operating system first checks to see if the data is in the cache before reading it from the disk. Because computers can access data from RAM much faster than from a disk, disk caching can significantly increase performance. Many cache systemsalso attempt to predict what data will be requested next so they can place that data in the cache ahead of time.
Although caching improves performance, there is some risk involved. If the computer crashes (due to a power failure, for example), the system may not have time to copy the cache back to the disk. In this case, whatever changes you made to the data will be lost. Usually, however, the cache system updates the disk frequently so that even if you lose some data, it will not be much. Caches that work in this manner are called write-back caches. Another type of disk cache, called a write-thru cache, removes the risk of losing data because it only caches data for read operations; writeoperations are always sent directly to the disk.
Stay up to date on the latest developments in Internet terminology with a free weekly newsletter from Webopedia. Join to subscribe now.
We look at a few of the more troubling aspects of statistics and how these may be used to advance an agenda or skew the facts to someone's... Read More »29 Free Android Apps for Cash-Strapped Students
From wacky alarm clocks to lecture hall tools and after class entertainment, these Android apps are a good fit for a student's life and budget. Read More »Sharing Threat Intelligence
A growing number of startups make the sharing of threat intelligence a key part of their solutions. Read More »
The Open System Interconnection (OSI) model defines a networking framework to implement protocols in seven layers. Use this handy guide to compare... Read More »Network Fundamentals Study Guide
Networking fundamentals teaches the building blocks of modern network design. Learn different types of networks, concepts, architecture and... Read More »Computer Architecture Study Guide
This Webopedia study guide describes the different parts of a computer system and their relations. Read More »