Re: read vs write

[Stefan Smietanowski <stesmi@stesmi.com>]

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Saswat Praharaj wrote:
> yups I meant MBps ..thanks for correcting me .
> 
> However, I dont agree with your ford/road example.
> 
> I just checked the product specification of STA340016A (seagate) . 
> 
> Here is what they claim : 
> 
> [  This manual describes the functional, mechanical and interface specifi-
> cations for the ST380021A, ST360021A, ST340016A and ST320011A.
> These drives provide the following key features:
> · 7,200-RPM spindle speed and 2-Mbyte buffer combine for superior
>   desktop performance
> · High instantaneous (burst) data-transfer rates (up to 100 Mbytes per
>   second) using Ultra DMA mode 5 ]

Yes, burst is transfer speed not speed from the platter.

The drive has a cache (2MB). From that cache you can transfer
at 100MB/s, not from the platter sadly enough. Even those 10kRPM
drives don't do 100.

So road == cable == from cache in a sense (assuming the cache can
do 100MB/s).
T-Ford = platter.

I wish it was different but it's not.

I mean, a SATAII-300 - do you honestly believe you can read and write
att 300MB/s to that drive? To/From Cache : maybe. Platter : No way.

But if you read the same data 10 times in a row (size=1MB let's say)
then yes, you should be seeing 100MB/s or somewhere close depending on
where your controller is, how saturated the bus is, etc.

// Stefan
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