WEBVTT - Why does my hard drive make that churning sound?

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<v Speaker 1>Welcome to brain Stuff from how stuff works dot com

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<v Speaker 1>today's question, what is the churning sound I hear from

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<v Speaker 1>my hard drive whenever it's retrieving data. Let's say you

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<v Speaker 1>do something simple like you double click on the icon

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<v Speaker 1>for a spreadsheet file. This simple act on many computers

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<v Speaker 1>can take ten or twenty seconds to complete, and all

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<v Speaker 1>during that time, the hard disc is churning away. The

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<v Speaker 1>hard disc access light flickers, and the drive might make

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<v Speaker 1>a horroring rumbling or high pitched whinding noise. If the

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<v Speaker 1>mechanism in the drive is loud, you definitely know that

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<v Speaker 1>something is going on inside the drive. There's an arm

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<v Speaker 1>that holds the read write heads. This arm can move

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<v Speaker 1>the heads two tracks near the hub or near the

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<v Speaker 1>edge of the disk. A normal hard disc is five

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<v Speaker 1>inches or less than diameter, so this arm can move

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<v Speaker 1>about two inches across the face of the disk. The

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<v Speaker 1>speed at which this arm can move is astonishing. The

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<v Speaker 1>arm is very light and its actuator is powerful and precise.

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<v Speaker 1>The arm can slide across the face of the disc

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<v Speaker 1>hundreds of times per second if it needs to. If

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<v Speaker 1>you think about how a speaker works, this isn't much different.

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<v Speaker 1>A speaker is moving a lightweight cone back and forth

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<v Speaker 1>hundreds of times per second to generate sound. As the

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<v Speaker 1>hard disc arm moves back and forth rapidly, it sets

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<v Speaker 1>up vibrations that our ears here as sounds. Why when

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<v Speaker 1>you click on a simple spreadsheet file would the disks

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<v Speaker 1>heads have to move so much ten or twenty seconds

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<v Speaker 1>worth of movement. Sometimes there are two things that cause

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<v Speaker 1>all the movement. First, to start a spreadsheet application like Excel,

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<v Speaker 1>the hard disc cast to load the application itself, along

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<v Speaker 1>with a number of libraries that support the application. The

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<v Speaker 1>total size of all these different files might be many megabytes,

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<v Speaker 1>and the files are scattered all over the disk. Loading

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<v Speaker 1>twenty or thirty megabytes of data takes time and requires

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<v Speaker 1>the disc head to move thousands of times to retrieve

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<v Speaker 1>all the pieces. The data file itself has to load also,

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<v Speaker 1>and that's the second thing. The operating system has to

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<v Speaker 1>move the head to the drive's directory to find the folder,

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<v Speaker 1>make sure that the file name exists, and then discover

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<v Speaker 1>the location of the file. Then the operating system needs

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<v Speaker 1>to read dozens of tracks scattered all over the drive

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<v Speaker 1>to access to the file altogether. Clicking on a single

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<v Speaker 1>icon may cause the disc heads to reposition themselves thousands

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<v Speaker 1>of times in the process. This is why you hear

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<v Speaker 1>the drive churning. It's doing a lot of work. Do

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<v Speaker 1>you have any ideas or suggestions for this podcast? If so,

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<v Speaker 1>please send me an email at podcast at how stuff

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<v Speaker 1>works dot com. For more on this and thousands of

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