I'm Amazed: How Do Hard Drives Simultaneously Perform Different Tasks?

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In summary, the ability of a computer's hard drive to simultaneously delete, read, and download files from different locations is achieved through the use of multiple read/write heads and fast seek times. However, performing multiple read actions at the same time can cause a decrease in performance, especially if the hard drive is fragmented. It is also not recommended to perform multiple read actions at once due to the potential impact on the hard drive's lifespan.
  • #1
peter.ell
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Actually, I understand the basics of how hard drives work, my question is more specific. I'm curious as to how a computer's hard drive can simultaneously delete files, read files, and download files all to/from different places on the hard drive.

It can't just be due to a fast-moving head, it can't possibly move fast enough to do all those things for multiple files at the same time, right? If it can, how in the world did engineers get a hard drive to read and write to many different places so quickly?

Our ability to create things just boggles my mind!
 
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  • #2
peter.ell said:
Actually, I understand the basics of how hard drives work, my question is more specific. I'm curious as to how a computer's hard drive can simultaneously delete files, read files, and download files all to/from different places on the hard drive.

It can't just be due to a fast-moving head, it can't possibly move fast enough to do all those things for multiple files at the same time, right? If it can, how in the world did engineers get a hard drive to read and write to many different places so quickly?

Our ability to create things just boggles my mind!
It helps that the read/write head actually has multiple heads. They all move in unison, true, but one can be reading while another is writing.

Beyond that, though, yes. They are just incredibly fast.

You can read a little about it: http://en.wikipedia.org/wiki/Hard_disk_drive#Data_transfer_rate

BTW, they actually only have 2 actions: read and write.
Deleting is simply removing (overwriting) the pointer to the file. It doesn't actually touch the file.
Downloading is not a hard drive thing. That's a network thing.
 
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  • #3
Most quick actions are done from within RAM where there are no moving components. Then when speed is not so critical it writes to the HD. However most HDs are now at least 7200RPM which is quite fast.
 
  • #4
DaveC426913 said:
It helps that the read/write head actually has multiple heads. They all move in unison, true, but one can be reading while another is writing.
Hard drives, at least the ones used on PC's don't do that anymore. Because of the high track densities and the fact that servo patterns are created by other devices, the tracks from surface to surface are no longer lined up. It takes longer to switch heads and reposition the head to track center than it does to step across a surface by 1 track and recenter the head.

With average seek times at 10ms or less, and at 7200 rpm (or in some cases 10,000 rpm), the total seek time isn't too long and the drives can random access fairly well. There is also read ahead and write behind caching going on in the drives and also in the computer (depending on the OS). The main improvement has been in streaming transfer rates because of the increasing bit densities.
 
  • #6
This is one is good also. The narrator explains what's going on.



This one explains the action at the head level with Flash/Java demos on the right

http://www.research.ibm.com/research/gmr/basics.html
 
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  • #7
Besides how this mechanism works, I have another question about reading two or more files simultaneously from a hard drive.

Isn't this bad to burn a DVD from an HDD and at the same time try to open different files and listen to music and ... from that same drive?

I say that because when I'm burning a DVD from my external drive and try to play a video file or copy from my HDD at the same time, the Writing Buffer decreases to zero or the video files I try to play have little interruptions when playing.

I don't think it's because of my system components. my external HDD is USB 3.0 and I have Windows 7 HP and a Dell XPS 15 L502x with Core i7 and 6 GBs of RAM and my burning software is Nero which is a professional tool. Is this normal?

I'd be very thankfull if someone could help.
 
  • #8
cheraidnist said:
Besides how this mechanism works, I have another question about reading two or more files simultaneously from a hard drive.
A hard drive can't do multiple reads simultaneously. It's reading data from one location at a time. It can anticipate further reads from that same area later with read ahead buffering to reduce the amount of random accessing. A hard drive's data rate is much slower if it has to do a lot of random accesses.

Isn't this bad to burn a DVD from an HDD and at the same time try to open different files and listen to music and ... from that same drive?
Depends on the data rate required to burn the DVD versus the effect data rate of the HDD if it's doing a lot of random accessing, but yes, it's probably a bad idea. The DVD burning program should set it's priority higher than normal (you can check this with task manager), so that the music or video would get interrupted, instead of the DVD burn process, which I think needs to be continous. If you have multiple hard drives, then burning the DVD from one hard drive while watching a video from a different hard drive should not be an issue.
 
  • #9
Thanks a lot rcgldr. i hope it would be helpful to use priority options of task manager. There is also some third party software from Microsoft that does the task more professionally, i do not remember the name.

About reading two files at the same time, which is not exactly a simultaneous read action as was mentioned in previous posts, i think even if the read rate is not high, it's not a good idea to do this, specially if the hard drive is fragmented. because Drive Head should move between sectors so many times to read and buffer a file in one place and go back to read and buffer the remaining of the other file and so on. Since HDD life expectancy depends specifically on Drive Head moves, i think it will reduce the life span very much.
 
  • #10
Buffering the right thing at the right time can do wonders. That's part of the so-called "mystery".
That's a technique you'll encounter EVERYWHERE in the business of processing data. For instance your DVD burn software probably buffers some amount of data from the slower access HDD to your RAM. Browsers buffer data from the slower internet medium to the faster local HDD. Your processor buffers data from the slow RAM(comparatively) to its own fast registers.

And this piece of software you are referring to doesn't do it "more professionally", it just gives you more information and looks fancier that your average task manager.
It is also called "Process Explorer" and is an incredible piece of software for monitoring just about everything your computer is doing in real time.
 
  • #11
Sorry, this thread was originally posted almost two months ago. The technology has changed. All answers are no longer valid.
 

1. How does a hard drive store data?

A hard drive stores data using magnetism. It has a spinning platter coated with a magnetic material, and an arm with a magnetic head that reads and writes data onto the platter. When data is written, the head aligns the magnetic particles in a specific pattern, representing the data. When data is read, the head detects the magnetic pattern and translates it into readable data.

2. What is the difference between a hard drive and solid state drive?

A hard drive uses mechanical components, such as spinning platters and a moving arm, to store and retrieve data. A solid state drive (SSD) uses flash memory chips to store data, similar to a USB drive. This makes SSDs faster and more durable than hard drives, but also more expensive.

3. How does a computer access data on a hard drive?

When a computer needs to access data on a hard drive, it sends a request to the hard drive's controller. The controller retrieves the data from the appropriate location on the platter and sends it to the computer's memory for processing. The speed at which this process occurs depends on the read/write speed of the hard drive.

4. How much data can a hard drive hold?

The amount of data a hard drive can hold depends on its storage capacity, which is measured in gigabytes (GB) or terabytes (TB). A typical hard drive can hold anywhere from 500 GB to 4 TB of data, but larger capacities are becoming more common as technology advances.

5. How do I know when my hard drive is failing?

There are several signs that indicate a hard drive may be failing, such as slow performance, frequent crashes or errors, unusual noises coming from the hard drive, and files becoming corrupted or inaccessible. It's important to regularly back up important data in case of hard drive failure.

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