[ale] A little math

[Scott Castaline]

On 02/10/2010 12:46 PM, JK wrote:
> On 2/10/2010 10:14 AM, Sean McNealy wrote:
>> Testing to a file on my machine (no raid going on)
>> 512000000 bytes (512 MB) copied, 81.1661 s, 6.3 MB/s
>>
>> extrapolation: 1TB @ 6.3 MB/s is 44 hours.  Wow, that is a long time.
>>
>> I forget the relevant specs for this machine, but for comparison
>> copying that same 512MB file was:
>> 512000000 bytes (512 MB) copied, 7.091 s, 72.2 MB/s
>
>
> What are you comparing to?
>
> In theory, a SATA 3 drive on a SATA 3 interface should be able to
> push 300MB/s, which would get you through a whole TB in about
> an hour.  Even the fastest pre-SATA drives are going to be at
> least 10x slower, and if it's a USB drive, slower yet. 8 days
> seems really slow, though.  You haven't got it hanging off a
> USB 1.0 interface by any chance?
>
> -- JK, putting to use knowledge gained through recent experience.
>
>
Nope, it's my 4th internal drive SATAII. The numbers that I've found 
don't specify the machine just that the drive was a SATA internal 500GB. 
It didn't give details as to what brand, I or II or MoBo specs. I 
believe it was a fairly recent post, about 6 to 9 months ago. I think he 
was saying that it slows the write down because urandom is very CPU 
intense. I've also noticed that it doesn't seem to be multithreaded 
either as CPU core 0 sits about 10% while CPU core 1 is at a steady 100% 
with every once in a while drop to 50% for very short periods. I'll try 
to find the post again and provide the link if you'd like to check it out.