Hard drive speed

[ex_reven]

Redid it...pretty much the same result

[nora.e]

Originally Posted by mas0n

This is because the entire disk is read from start (outside) to finish (inside) and the outside tracks will always read faster because they are spinning at a higher rate of speed than the inner tracks.

how is this posible? if a wheel is turning at 7,200rpm at the outer edge, and solid and has no flex, it will also still be turning at 7,200rpm at the center hob area.

[ex_reven]

Originally Posted by nora.e

how is this posible? if a wheel is turning at 7,200rpm at the outer edge, and solid and has no flex, it will also still be turning at 7,200rpm at the center hob area.

No, use your head. Think about it.
The outer part is moving faster. If I swing my arm to throw a punch the bit of my arm a few cm from my shoulder only moves a few cm while my hand has moved about 4 feet in the same period of time.

Say it takes me 1 second to throw the punch. My fist is travelling at 4 feet per second, and that topmost part of my arm near the shoulder is travelling at say 5cm/sec.

Roughly:
Hand = 120.4cm/sec
Top of arm = 5cm/sec

Hand = 433440cm/hour
Arm = 18000cm/hour

Hand = 4.3km/hour
Arm = 0.18km/hour

My hand is to the arm what the outer edge of the disk is to the inner edge of the disk.
While my hand rotates around my shoulder, the outer edge of the disk rotates around the centre of the disk. They both operate around a central point.

[driver66]

LOL roll a paper cup on the floor and see which end is traveling faster
That's a simpler way to explain it

[ex_reven]

Woah...sorry about this double post but I just hit a extremely anomalous result.
I ran HDtach again after finding and removing the jumper on both hard drives (which theoretically changes it from Sata 1.5gb/s to Sata 3gb/sec) and look at my new result



LOL driver! Your analogy works better

[nora.e]

Originally Posted by driver66

LOL roll a paper cup on the floor and see which end is traveling faster
That's a simpler way to explain it

Ya but if you stick a pencil threw it lenth wise an spin the pencil both ends are traveling at the same rate of speed again.

[ex_reven]

Originally Posted by nora.e

Ya but if you stick a pencil threw it lenth wise an spin the pencil both ends are traveling at the same rate of speed again.

I dont get it? Think of it this way, anything that travels a different distance in the same amount of time is travelling at a higher speed. The outer edge of the disk travels further because its circumference is greater than the inner edge.

[nora.e]

Originally Posted by ex_reven

No, use your head. Think about it.
The outer part is moving faster. If I swing my arm to throw a punch the bit of my arm a few cm from my shoulder only moves a few cm while my hand has moved about 4 feet in the same period of time.

Say it takes me 1 second to throw the punch. My fist is travelling at 4 feet per second, and that topmost part of my arm near the shoulder is travelling at say 5cm/sec.

Roughly:
Hand = 120.4cm/sec
Top of arm = 5cm/sec

Hand = 433440cm/hour
Arm = 18000cm/hour

Hand = 4.3km/hour
Arm = 0.18km/hour

My hand is to the arm what the outer edge of the disk is to the inner edge of the disk.
While my hand rotates around my shoulder, the outer edge of the disk rotates around the centre of the disk. They both operate around a central point.

what you're desribing here is more an isue of leverage, not speed. If you extend your arm out to the side and turn at the waist half way around both your hand and your sholder have done the same thing, make a half of a revolution.

[ex_reven]

Originally Posted by nora.e

what you're desribing here is more an isue of leverage, not speed. If you extend your arm out to the side and turn at the waist half way around both your hand and your sholder have done the same thing, make a half of a revolution.

Leverage is much more focused on energy efficiency through changing fulcrums. The fulcrum in this case is the centre of the disk. It is the leverage that achieves the different speeds, which brings us back to the point that the outside of the disk is indeed faster.

Another (more stable looking) result:

[nora.e]

I don't see us coming to an agreement on this one

[ex_reven]

Originally Posted by nora.e

I don't see us coming to an agreement on this one

thats ok, you can have your opinion
Back to the point it sprung from, the whole "my graph should be a curve rather than be going upwards after its starting position because the disk spins slower as it moves away from the edge" comment made by mas0n.

Why isnt mine doing it? I can see in everyone elses results that were posted that they had the symptoms he described.

[mas0n]

It's simple if you break it down.

The entire disk must spin at 7200RPM.

The outer tracks are longer than the inner tracks.

The outer tracks therefore would allow for more data to be read in a single rotation.

Also, If you have an 12 speed bicycle and peddle at the same rate through all 12 speeds, the 12th speed (the one with the largest gear) allows for the highest speed.

[driver66]

Originally Posted by nora.e

Ya but if you stick a pencil threw it lenth wise an spin the pencil both ends are traveling at the same rate of speed again.

This is all my old beast does It seems ok.

[GLD]

@ ex reven

I see you are running 250g and 320g hdd's in your raid 0. Isn't it considered best to run matching capacity hdd's? Could this be the cause of the anomaly you are seeing?

[ex_reven]

Originally Posted by GLD

@ ex reven

I see you are running 250g and 320g hdd's in your raid 0. Isn't it considered best to run matching capacity hdd's? Could this be the cause of the anomaly you are seeing?

well, looking at my last benchmark my average sequential read speed seems alot more steady.
As for matching hard drives, im pretty sure the size isnt a problem, since they are partitioned evenly anyway. Id say that them being the same model drive (7200.10 in this case) in comparison to two different models has a bigger impact on performance.

[mas0n]

do both use perpendicular recording?

[ex_reven]

Originally Posted by driver66

This is all my old beast does It seems ok.

Lookin good

Originally Posted by mas0n

do both use perpendicular recording?

My drives? Both of them are 7200.10, so yes. I should buy a third. These things are pretty damn cheap too.

[mas0n]

What confuses me is that it looks like it is a bottleneck at the controller but your burst speeds are right where they should be.

[ex_reven]

Originally Posted by mas0n

What confuses me is that it looks like it is a bottleneck at the controller but your burst speeds are right where they should be.

I thought the same.
I wonder how much benefit a hardware based controller would provide then on my particular setup.

[hat]

Ok, NOW you're showing off

[ex_reven]

nope...pinchys score still pwns mine

[Wile E]

Originally Posted by nora.e

how is this posible? if a wheel is turning at 7,200rpm at the outer edge, and solid and has no flex, it will also still be turning at 7,200rpm at the center hob area.

Yes, they will be rotating at the same speed, but the outside edge must travel a greater distance than the inside hub, to make one complete rotation. Therefore, the surface speed of the outer edge is greater. IE: The drive head passes across more data per rotation on the outer edge, compared to the inner edge.

@Reven - Those new benches are looking better. The different sized drives could cause the discrepancies, when compared to others.

[regan1985]

speeds are also different due to what your running like my onboard runs at 94mb but on my pci ex runs at 98mb and if i had a good controler i could probibly get 108mb, but burst speeds dont really matter unless you are moving loads of small 1k files, its better to have a line that curve down on a gentle slope and have a read time of under 13,

[Verikon]

Errr... I don't like that downward trend near the end. I want magic SATAII jumpers on my HDDs!


No fair...

[TXcharger]

wow pitiful mine was under 60mb/s at all times and had random drops with a huge curve