fastest raw device copy?

[Christoph Kukulies]

Jeremy Chadwick schrieb:
> On Fri, Oct 31, 2008 at 03:36:02PM +0100, Christoph Kukulies wrote:
>   
>> Ivan Voras schrieb:
>>     
>>> Jeremy Chadwick wrote:
>>>   
>>>       
>>>> On Fri, Oct 31, 2008 at 09:48:16AM +0100, Christoph Kukulies wrote:
>>>>     
>>>>         
>>>   
>>>       
>>>>> What would be the fastest way to do that sector by sector copy? I'm 
>>>>>  using dd right now,
>>>>>
>>>>> dd if=/dev/ad0 of=/dev/da0 bs=10000000
>>>>>       
>>>>>           
>>>   
>>>       
>>>> On the flip side, your blocksize (bs) there is quite high for no good
>>>> reason.  I'd pick something more like bs=64k or bs=128k.  The default
>>>> (512) is too small for what you want, but 10MBytes is silly.
>>>>     
>>>>         
>>> Not only that, but "10000000" isn't even correct - it needs to be a
>>> multiple of sector size. Generally, using suffixes will do the right thing:
>>>
>>> dd if=/dev/ad0 of=/dev/da0 bs=1m
>>>
>>>   
>>>       
>> OK, I understand that 10000000 isn't good, I just thought it wouldn't  
>> harm. But if it is a transfer rate killer then I'd better think of  
>> typing ^C now. The command is running for 6 hours now.
>>     
>
> Six hours?  Hmm...  That seems too long, but of course the FreeBSD USB
> stack is involved, and a USB device in general.  I would have assumed
> that copy should have finished after 2-3 hours tops.
>
>   
>> An idea how I can check the current amount of transfered byed alongside  
>> the running dd command? Or watch the current i/o rate?
>>     
>
> iostat or gstat (I'm willing to bet you prefer the latter) will get you
> what you want, more or less.
>
>   


The job just finished and I have a figure of the Ubuntu performance, 
with the unfortunate blocksize parameter though, so I think it isn't 
much worth. Anyway here is the figure of the
above dd command copying 500GB to a WDC disk in an Icy box.

50010+1 Datensätze ein
50010+1 Datensätze aus
500107862016 Bytes (500GB) kopiert, 25787,9 s, 19,4 MB/s

Will do that using FreeBSD next time.

Thanks a lot so far.

--
Christoph