Some Unix benchmarks for those who are interesed

[Fluffles]

Ivan Voras wrote:
> Fluffles wrote:
>
>   
>> If you use dd on the raw device (meaning no UFS/VFS) there is no
>> read-ahead. This means that the following DD-command will give lower STR
>> read than the second:
>>
>> no read-ahead:
>> dd if=/dev/mirror/data of=/dev/null bs=1m count=1000
>> read-ahead and multiple I/O queue depth:
>> dd if=/mounted/mirror/volume of=/dev/null bs=1m count=1000
>>     
>
> I'd agree in theory, but bonnie++ gives WORSE results than raw device:
>   

On what hardware is this? Using any form of geom software RAID?

The low Per Char results would lead me to believe it's a very slow CPU;
maybe VIA C3 or some old pentium? Modern systems should get 100MB/s+ in
per-char bonnie benchmark, even a Sempron 2600+ 1.6GHz 128KB cache which
costs about $39. Then it might be logical DD gets higher results since
this is more 'easy' to handle by the CPU. The VFS/UFS layer adds
potential for nice performance-increases but it does take it's toll in
the form of cputime overhead. If your CPU is very slow, i can imagine
these optimizations having a detrimental effect instead. Just guessing here.

Also, checkout my benchmark results i posted in response to Andrei Kolu
in particular the geom_raid5 benchmark; there the UFS/VFS layer causes
25% lower write performance; due to cpu bottlenecks (and some UFS
inefficiency with regard to max blocks per cylinder). So for all i know
it may be just your CPU which is limiting sequential performance somewhat.

Regards,

- Veronica