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Old 02-26-2011, 09:09 AM   #1
elishac
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hard disk speed


hello,

when the disk is graphically represented as a rectangle (such as in gparted or in the Microsoft windows disk manager), where is the disk the fastest to read and write ? Is it on the left or on the right ?

thanks
 
Old 02-26-2011, 11:08 AM   #2
unSpawn
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While I doubt there's graphical applications of this type that cater for those reading right-to-left, in left-to-right visual read mode a disk is represented left-to-right (doh), where left is the "center" of the disk (with a marginally greater relative speed) and right the "edge". (Also see disk caching, degrading performance by slaving, motherboard chipset selection by connector, elevator and schedulers, file system choice, creating write-intensive partitions on different physical disks et cetera.)
 
Old 02-26-2011, 11:39 AM   #3
elishac
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Hello,

thanks for your answer. You touched quite a lot of different topics, which is nice, but could you please try to explain them a little bit more in depth?
I'm basically just wondering where I should put my OS and my data in a 2 partition drive (I want my OS to have the greater speed).

Also, are you sure about your assessment concerning the fact that the center of the disk is where it is the fastest ? I would have thought quite the opposite from my newbie point of view...

kind regards.
 
Old 02-26-2011, 11:43 AM   #4
stress_junkie
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I believe that unSpawn misspoke. The edge of the disk moves faster than the center. That means that data can transfer faster when it is located near the edge of the disk.

In the rectangular representation of the disk in a disk partitioning tool it is clear to me that the left side of the rectangle represents the edge of the disk.

The edge of the disk is the beginning of the disk.

The opposite is true in CD and DVD media. They start reading and writing near the center of the disk and move outward toward the edge.

http://www.linuxquestions.org/questi...9/#post4270334

Last edited by stress_junkie; 02-26-2011 at 11:50 AM.
 
Old 02-26-2011, 11:52 AM   #5
unSpawn
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Yeah, I got it reversed, thanks for correcting me!
 
Old 02-26-2011, 12:12 PM   #6
elishac
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So I should place my OS on the left of the rectangle, and my data on the right ? (assuming that my data doesn't need as high performances as the OS).

Could I please have some more explanations regarding the notions that were used above (disk caching, degrading performance by slaving, motherboard chipset selection by connector, elevator and schedulers, file system choice, creating write-intensive partitions on different physical disks et cetera) ?
How are these relevant and how do they affect my choice ?



Thanks

Last edited by elishac; 02-26-2011 at 03:19 PM.
 
Old 02-26-2011, 03:19 PM   #7
elishac
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I was also wondering if it is possible to know which platter is considered, as it might be that in a drive that consists of 2 platters, a OS that is at 50% of the rectangle has actually a higher performance than one that is at 20%, if you see what I mean (since it's at the edge of the second platter).

One last question: are there any numbers on that speed difference ? How much % do I gain by writing in the edge rather than in the middle ?

Thanks
 
Old 02-26-2011, 03:27 PM   #8
stress_junkie
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Quote:
Originally Posted by elishac View Post
So I should place my OS on the left of the rectangle, and my data on the right ? (assuming that my data doesn't need as high performances as the OS).
That is a question for you to answer. What I mean is that we all have our performance tuning rules. You should experiment to decide if there is a significant change in performance with one configuration over another. I doubt that you will find any.
Quote:
Originally Posted by elishac View Post
Could I please have some more explanations regarding the notions that were used above (disk caching, degrading performance by slaving, motherboard chipset selection by connector, elevator and schedulers, file system choice, creating write-intensive partitions on different physical disks et cetera) ?
How are these relevant and how do they affect my choice ?
These are all complicated issues. You could use Google to research them and then determine how they should affect your decisions. In most circumstances all of these issues are academic.
 
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Old 02-26-2011, 03:40 PM   #9
stress_junkie
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Quote:
Originally Posted by elishac View Post
I was also wondering if it is possible to know which platter is considered, as it might be that in a drive that consists of 2 platters, a OS that is at 50% of the rectangle has actually a higher performance than one that is at 20%, if you see what I mean (since it's at the edge of the second platter).
Both platters are used equally. The concept of cylinders that go through the platters is useful to understand how disk drives store data. The outer track on each platter combined with the outer track of the other platters nearest the edge are considered to be one cylinder. The all of the second track on each platter combined are considered to be cylinder 2. All of the third tracks on all of the platters combined are considered to be cylinder 3. And so on. So all of the outer tracks on all of the platters get used before any of the inner tracks get used if you are writing sequentially to the disk.

Additionally there is the complication that disk drive controllers hide the actual geometry of the disks from the operating system. Look up "Logical Block Assignment" also called LBA.
Quote:
Originally Posted by elishac View Post
One last question: are there any numbers on that speed difference ? How much % do I gain by writing in the edge rather than in the middle ?
If you go to the post that I referenced above in #4 you will see a test that will show a way to see this for yourself. However, in real life on a desktop computer, this is not relevant. The disk drive is usually not heavily loaded on workstation computers. So again, this is all academic unless you are designing a computer to record real time data from an atom smasher or a computer to run all of the credit card transactions for a large bank. Short of those kinds of computer workloads you will not see any difference in performance from one configuration to another. Hardware (CPU, memory, and motherboard chip sets) will make a difference in workstation performance but even that is not predictable. I have put together combinations of motherboard/CPU/RAM that worked great while others that seemed equally promising performed badly.

In summary: the placement of the software on the disk will not significantly affect the performance of a typical workstation running a typical workload.

Last edited by stress_junkie; 02-26-2011 at 03:45 PM.
 
Old 02-26-2011, 07:14 PM   #10
jefro
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The problem is two fold. One is data but the hard drive has to go back and forth between where the data is and where the location to look is. OS/2 introduced to home computers a way to put the file info in the middle of the disk and then put data on both sides of it. That way the heads could move less and they felt that the movement of the heads took the most time no matter how well the data was placed.
 
  


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