Quiet computer

[David King]

Here's another run that doesn't have a constant number of bytes, so  
the bytes/sec might be a little more accurate

~% for BS in 1 512 $(expr 1024 \* 4) $(expr 1024 \* 16) $(expr 1024  
\* 64); do dd if=/dev/random of=/dev/null bs=$BS count=1024;  
done                                              1024+0 records in
1024+0 records out
1024 bytes transferred in 0.395678 secs (2588 bytes/sec)
1024+0 records in
1024+0 records out
524288 bytes transferred in 0.791416 secs (662468 bytes/sec)
1024+0 records in
1024+0 records out
4194304 bytes transferred in 6.415680 secs (653758 bytes/sec)
1024+0 records in
1024+0 records out
16777216 bytes transferred in 25.814593 secs (649912 bytes/sec)
1024+0 records in
1024+0 records out
67108864 bytes transferred in 102.280978 secs (656123 bytes/sec)



On 16 Oct 2006, at 10:14, David King wrote:

>> BTW, David, test (if you have enough time for curiosity) /dev/ 
>> urandom (or
>> wherever the generator is) with different values of 'bs', from very
>> small to large (1 byte, 512, 4k, 16k, 64k) to see how much it depends
>> on block size.
>>
>>> bash-2.05b$ time dd if=/dev/urandom bs=1024 count=10240 of=/dev/null
>>> 10240+0 records in
>>> 10240+0 records out
>>> 10485760 bytes transferred in 0.154649 secs (67803598 bytes/sec)
>
>
> ~% cat test_rand_block.sh
> #!/usr/local/bin/bash
>
> for BS in 1 512 $(expr 1024 \* 4) $(expr 1024 \* 16) $(expr 1024 \*  
> 64); do
>         COUNT=$(expr $(expr 1024 \* 64) / $BS)
>         BYTES=$(expr $COUNT \* $BS)
>
>         echo bs=$BS count=$COUNT bytes=$BYTES
>
>         dd if=/dev/random of=/dev/null bs=$BS count=$COUNT
>
>         echo ------;
> done
> ~% sh test_rand_block.sh
> bs=1 count=65536 bytes=65536
> 65536+0 records in
> 65536+0 records out
> 65536 bytes transferred in 25.599306 secs (2560 bytes/sec)
> ------
> bs=512 count=128 bytes=65536
> 128+0 records in
> 128+0 records out
> 65536 bytes transferred in 0.099902 secs (656003 bytes/sec)
> ------
> bs=4096 count=16 bytes=65536
> 16+0 records in
> 16+0 records out
> 65536 bytes transferred in 0.100660 secs (651062 bytes/sec)
> ------
> bs=16384 count=4 bytes=65536
> 4+0 records in
> 4+0 records out
> 65536 bytes transferred in 0.099324 secs (659820 bytes/sec)
> ------
> bs=65536 count=1 bytes=65536
> 1+0 records in
> 1+0 records out
> 65536 bytes transferred in 0.099681 secs (657458 bytes/sec)
> ------
>
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--
David King
Computer Programmer
Ketralnis Systems