writing large files quickly

[rbt]

Grant Edwards wrote:
> On 2006-01-27, rbt <rbt at athop1.ath.vt.edu> wrote:
> 
> 
>>I've been doing some file system benchmarking. In the process, I need to 
>>create a large file to copy around to various drives. I'm creating the 
>>file like this:
>>
>>fd = file('large_file.bin', 'wb')
>>for x in xrange(409600000):
>>     fd.write('0')
>>fd.close()
>>
>>This takes a few minutes to do. How can I speed up the process?
> 
> 
> Don't write so much data.
> 
> f = file('large_file.bin','wb')
> f.seek(409600000-1)
> f.write('\x00')
> f.close()

OK, I'm still trying to pick my jaw up off of the floor. One question... 
  how big of a file could this method create? 20GB, 30GB, limit depends 
on filesystem, etc?

> That should be almost instantaneous in that the time required
> for those 4 lines of code is neglgible compared to interpreter
> startup and shutdown.