# Why do hard disk drives partitions have different speed in read/writes?



## Master (Sep 25, 2015)

Hello Everyone, 
I recently purchased a new hard disk drive a 1 Terabyte to be exact. 
I ran a few tests using HdTunePro and noticed that the speed difference between partitions is some what noticeable . 
I partitioned my HDD like this 
Dirve C : 160G 
Drive D: 325G
Drive E: 325G
Drive F: 122G

I used file benchmark and saw that for the first partition the speed was almost 200MB/s and for the second drive it dropped to 190-199MB/s and for the 3rd partition it was 170~180MB/s and finally the last partition had the 110~118MB/s .
Why are they different ? whats the reason behind it ? 
Is it because the inner sections of Hard disk drives are denser than the outer sections ? 
I would be grateful if anyone could explain the reason behind this 
Thanks in advance


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## EarthDog (Sep 25, 2015)

Because of the location of the partitions/data on the platter... the inner part (beginning) is a lot smaller distance to travel around than the outer part (end). 

That said, the outer part is faster: http://superuser.com/questions/159890/does-the-order-of-partitions-matter


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## RCoon (Sep 25, 2015)

The closer to the centre of the platters you get, the slower the performance. If you spin at 7200rpm you can stick a lot of data in one row around the outside of the disk. At the very centre, the amount of data in that line is severely reduced, so the head has to read multiple lines for the same amount of data.


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## rtwjunkie (Sep 25, 2015)

Because the outer part of the HDD is the fastest.

This is why it was always recommended that if you put a paging file on an HDD, that you put it in the first partition.

I believe density is the same throughout the drive.

EDIT: LOL, 3 answers at the same time!


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## Master (Sep 25, 2015)

Thanks, but the density is the same everywhere, there is 512 for each sector, there are 63 sectors per each track and there are 255 tracks per each cylinder, so the data must be spread equally everywhere, and for inner sections, It should be faster since it takes lesser time to access any sectors compared to the outer sections


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## rtwjunkie (Sep 25, 2015)

Master said:


> Thanks, but the density is the same everywhere, there is 512 for each sector, there are 63 sectors per each track and there are 255 tracks per each cylinder, so the data must be spread equally everywhere, and for inner sections, It should be faster since it takes lesser time to access any sectors compared to the outer sections


 
No. As @RCoon was explaining, the track is shorter on the inner part.  Therefore, the same data might have to be on several tracks there less area to record the data), which means the head has to move.  Head movement is the slowest part of the operation.

On the outer edge, the head may not have to move, just reading along the same track.  Make sense?


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## Master (Sep 25, 2015)

rtwjunkie said:


> No. As @RCoon was explaining, the track is shorter on the inner part.  Therefore, the same data might have to be on several tracks there less area to record the data), which means the head has to move.  Head movement is the slowest part of the operation.
> 
> On the outer edge, the head may not have to move, just reading along the same track.  Make sense?


Its weird though!, windows System information reports that all tracks are the same, How can this even be possible when all tracks has exactly 63 sectors in them and each sector has 512 bytes in them! ?


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## RCoon (Sep 25, 2015)

Master said:


> Its weird though!, windows System information reports that all tracks are the same, How can this even be possible when all tracks has exactly 63 sectors in them and each sector has 512 bytes in them! ?



If every row on a platter was the same length, your hard drive would be a square.


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## Master (Sep 25, 2015)

I finally found it, you guys were right . 
thats the logical block addressing windows reports . hard disk drives has something called zone-bit recording, which means there  can be different zones inwhich every tracks can have different number of sectors. 
for example in zone 0 which resides in the outer regions on platter, there are more sectors per each track. and zone 1 has fewer number of sectors per each track and this goes on like this : 
I found it here : http://www.snia.org/education/storage_networking_primer/stor_devices/data_structure 
it has a great explanation .
Thanks again everyone.


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## FordGT90Concept (Sep 25, 2015)

This is not a scientific drawing but I think it will get the point across:






Remember, in HDDs, the RPMs are constant.  The less rotation the platter spins to retrieve/write the data, the faster it will read/write it.  Compare the blue arc in the picture to the red arc.  Blue should read/write more than twice as fast compared to the red arc.

Partitions will always be faster to slower going from the first created to the last created.

The same concepts apply to optical (CD/DVD/BluRay/LaserDisc/etc.) media.


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## Kursah (Sep 25, 2015)

Master said:


> Its weird though!, windows System information reports that all tracks are the same, How can this even be possible when all tracks has exactly 63 sectors in them and each sector has 512 bytes in them! ?



Hard drive's contain chipsets and control boards that not only control the interface but also allow them to convert what your OS sees from them. So sectors, tracks, etc. are all fudged to the interface so the OSes can read them and use them, the logic board controls where the data actually goes and how it gets there. This had to start happening years if not decades ago as drive sizes exceeded what current logic options were available for storage technology. There's some pretty interesting information if you research the history of the hard disk drive.

As said earlier, head movement is one of the big response issues with a mechanical hard disk drive, so closer to the outer edge is faster because of not needing to track as much and speed.



Edit: Also know that every single mechanical hard drive that we've created has bad sectors, the onboard controllers only report them through SMART when the limit is getting near so that the hard drive can be replaced. Tracking actual bad sectors on a HDD would be far scarier than most would ever want to see.


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## OneMoar (Sep 26, 2015)

better explanation
http://www.tomshardware.com/reviews/understanding-hard-drive-performance,1557-4.html


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