On 05/05/10 15:12, Phil Stracchino wrote:
> On 05/05/10 08:38, John Drescher wrote:
>    
>>> Sorry my servers are on gigabit links.
>>> How do you come to 9MB/s with a 100Mb link, is it not equals to 12,5 MB/s?
>>>        
>> Overhead.
>>
>>      
>>> If it's correct on a gigabit link I would have a rate transfer of 90MB/s
>>>        
>> You will probably get less than that if you do not use jumbo frames.
>>
>>      
I did an throughput test with iperf between 2 servers on a gigabit link 
and it results in a 940Mb/s transfer rate .
You tell me that transfer rate will be less than 90MB/s, is there so 
much overhead in the application layer?

>>> and the transfer rate of the sata disks are 3Gb/s(375MB/s).
>>>        
>> No way are your SATA drives that fast. More likely 1/4 to 1/3 of that
>> speed unless all servers are using high end SSDs.
>>      
> That.  Always remember that the data transfer rates specified on disk
> interfaces are the maximum burst transfer rate FROM a full disk cache or
> TO an empty one.  The actual sustained rates at which the physical
> mechanism can read or write data to and from the platters are FAR lower.
>
>
>    


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