DD not working--SUCCESS!

[Ian Malone]

Robert P. J. Day wrote:
> On Fri, 31 Aug 2007, Ian Malone wrote:
> 
>> Karl Larsen wrote:
>>> Jacques B. wrote:
>>>>  Because the clone would be of a
>>>> running system.  So booting from it would be comparable to booting
>>>> from a system that crashed (I'm making an educated guess at that one).
>>>>
>>>    Not a good guess. To use DD you need a computer with dd and a fast cpu. I
>>> did top while dd was working and it was taking 70% of the cpu's time :-P
>>>
>> It's one of the oldest Unix programs: it will copy as fast as your
>> system can go.  Yes, a fast system will copy faster.
> 
> i'm guessing he failed to provide a decent blocksize so dd was using
> the default blocksize of 512 bytes.  that will slow things down in a
> hurry.
> 

How would you go about estimating a decent blocksize (other than by
testing)?  My first instinct would be to go for some percentage of
the drive's cache.  (And it had better be a factor of the amount you
want to copy I suppose.)

-- 
imalone