file rawRead and rawWrite in chunks example

[Jay Norwood via Digitalmars-d-learn]

On Sunday, 9 August 2015 at 10:40:06 UTC, Nordlöw wrote:
> On Sunday, 9 August 2015 at 00:50:16 UTC, Ali Çehreli wrote:
>> Ali
>
> Now benchmarks write and read separately:
>
> 

I benchmarked my first results:
D:\visd\raw\raw\Release>raw
time write msecs:457
time read msecs:75

This is for 160MB of data. The write includes initialization of 
the values.

The read time is faster than my ssd drive, so I have to assume 
this is win7 or the ssd caching the data.

If I increase double count to 200,000,000 (to 1.6GB of data), the 
times are:
D:\visd\raw\raw\Release>raw
time write msecs:7236
time read msecs:11979

08/09/2015  10:12 AM     1,600,000,000 numberList.db

So that's around 220MB/sec for the writes and 133MB/sec for the 
reads.  That's an intel 520 series 180GB ssd, but in an SATA 
3Gb/s interface in a laptop.  Sequential write speed for that ssd 
should be about 257MB/sec.  Sequential read should be close to 
395MB/sec for this drive on a 6Gb/sec SATA.   So read speed is 
lower than I'd expect.

If I move this program over to my work computer, the same 1.6GB 
measurement returns these times below on a Samsung 840 SSD, which 
is on a 6Gb/sec SATA interface.  I believe the 458MB/sec write 
speeds. I suspect the read timing is again just measuring win7's 
cached data.

J:\visd>raw
time write msecs:3489
time read msecs:579