Webopedia on Google+Webopedia on TwitterWebopedia on FacebookTech Bytes Blog
Main » TERM » D »

disk cache

cache

)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.







TECH RESOURCES FROM OUR PARTNERS
DID YOU KNOW?
Hype Versus Action in the Developer's World

Often times technologies start as hype but with time become adopted. As a developer or technologist, it is worth reading the hype and knowing the... Read More »

Microsoft Hyper-V Network Virtualization Q&A

The top 5 Hyper-V questions with answers provided by Nirmal Sharma, a MCSEx3, MCITP and Microsoft MVP in Directory Services. Read More »

Storage Trends: Solid State and Software Defined

Solid state drives and software defined storage are two leading trends in the rapidly growing storage market.  Read More »

QUICK REFERENCE
How to Create a Desktop Shortcut to a Website

This Webopedia guide will show you how to create a desktop shortcut to a website using Firefox, Chrome or Internet Explorer (IE). Read More »

Flash Data Storage Vendor Trends

Although it is almost impossible to keep up with the pace of ongoing product releases, here are three recent highlights in the flash data storage... Read More »

15 Important Big Data Facts for IT Professionals

Keeping track of big data trends, research and statistics gives IT professionals  a solid foundation to plan big data projects. Here are 15... Read More »