Hard drive read speeds?

[imported_obgow]

On a hard drive the platter spins faster the further out from the center you go right? Would that make the data toward the outside of the platter read faster? If so is there a way to move the data to the outside?

 

[ghackmann]

Originally posted by: obgow
Would that make the data toward the outside of the platter read faster?

No.

 

[Gibsons]

Originally posted by: obgow
On a hard drive the platter spins faster the further out from the center you go right? Would that make the data toward the outside of the platter read faster? If so is there a way to move the data to the outside?

You can get higher transfer rates in outer zones.


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[Calin]

The platters rotate just as fast in inner zones as in the outer zones. However, the data density would decrease and the linear speed would increase. This is why "data zones" are used (they look like rings). So, in outer zones the data is written at similar data density (bytes/square inch) but it is presented faster to the read heads (or write heads).
A practical way to move the data to the outside would be to create partitions, and use the data that needs fast access to the outside of the disk, or considering the default Windows drive letter assigning, the "biggest" letter. However, take into account that starting from a "standstill", the inner tracks are closer than the outer tracks (not that would really affect the time needed for multiple reads, or long reads).

 

[Mark R]

This is correct, data transfer rates are generally higher at the outside edge of the platter, than at the centre.

The simple analysis is that the linear velocity at the edge is higher. However, it's not quite that simple. In order to improve reliability, the manufacturers divide up the platters into 'zones' where the length and width of the bits are changed. The aim is to keep the total number of bits / cm2 roughly constant.

So the higher linear velocity at the edge of the platter is partially compensated for by making the bits 'longer' and thinner. Typically, you see a see a smooth decrease in speed from the outer edge to the inner edge.

Higher speed drives, e.g. 10k rpm and 15k rpm drives use much smaller platters. Usually only around 2.5" for 10k and 2" for 15k, instead of 3.5" for slower drives. This means less change in speed from outer to inner edge.

The very latest hard drives use 'adaptive formatting' in order to maximize capacity and reliability. Each zone of side of each platter, is individually analysed and a format geometry (track spacing, bit length, etc.) is selected based on the exact measured properties of that zone. This means that you no longer get a smooth decrease from maximum to minimum transfer rate, instead it fluctuates wildly as you go from platter to platter and from zone to zone. Nevertheless, the overall trend is downwards as you approach the centre.

Hard drives are arranged so that they use the fastest part of the drive (the outer edge) first. The first files on the first partition will go into that area. So you could create 2 partitions - the first partition (usually C will go at the outer edge, and the 2nd (usually D will follow. You could put files which need high speed access on C, and files which just need bulk storage (and occasional use) on D.

If you can't divide your files simply into 2 groups, then there is little point partitioning. Partitioning is inefficient in terms of minimizing seek times, so unless you can get good benefits by seperating files into clear groups - you'll probably make things worse. For desktop use, seek time is generally more important than transfer rates.

 

[imported_whatever]

my impression is that they already do that - they start writing at the outside and go in, like an lp.

 

[WiseOldDude]

only if you put more info in the outer areas, which is not done. if it is spinning at 7200 RPM it still takes the same amount of time to make 1 revolution.

To the read head, the bits of data are going by the head at the same rate. The read head is blind to the fact that the bits of data are actually spread out further due to the greater circumference of tracks near the outside edge

 

[imported_obgow]

Thank you

 

[BitByBit]

Windows' defrag option to 'rearrange program files so applications start faster' moves the most frequently-used data to the edge of the platter, resulting in a speed increase.