phoronix benchmarks ext4 vs. btrfs

[David Quigley]

On 03/09/2012 08:42, Przemek Klosowski wrote:
> On 03/09/2012 01:43 AM, Adam Williamson wrote:
>> On Thu, 2012-03-08 at 22:19 -0700, Chris Murphy wrote:
>>> I'm not sure how useful 'time' is as a benchmark for file copies.
>>
>> Don't file transfers get cached and return to a console as 
>> 'complete'
>> long before the data is ever written, sometimes?
>>
>> I'm pretty sure you sometimes hit the case where you copy 200MB to a 
>> USB
>> stick, it returns to the console pretty fast, but the light on the 
>> stick
>> is still flashing, and if you run 'sync', it sits there for quite a
>> while before returning to the console, indicating the transfer 
>> wasn't
>> really complete. So I'm not sure 'time'ing a 'cp' is an accurate 
>> test of
>> actual final-write-to-device.
>
> That is true---but in that case, we could flush the disks. and then
> time the operation followed by another flush, i.e.:
>
> sync; time (cp ...; sync)
>
> I assume that the old-time Unix superstition of calling sync three
> times no longer applies :)
>
> Perhaps a dedicated disk benchmark like bonnie++ would be a better
> test, though.


If you want to look seriously into file-system benchmarking I would 
suggest looking into the work done by the fsbench people at Stony Brook 
University's Filesystem and Storage Lab (FSL). There is a survey paper 
there for the last decade of FS benchmarks and their short commings and 
what should be addressed.


http://www.fsl.cs.sunysb.edu/project-fsbench.html


Dave