On Sunday, 18 February 2018 11:16:04 GMT Ralph Corderoy wrote:
> dd(1) is quick. It read(2)s a block of bytes and write(2)s that block.
> The kernel does the transfer of bytes from the device to dd's memory and
> vica versa. If you don't choose a block size then it might be quite
> small,
>
>
> and most of your time is spent in overhead of switching between dd and
> the kernel. Using bs=1M would cut down that overhead as you're unlikely
> to be using a device that insists on a particular block size.
I'm now halfway through writing the first drive, so I'll let that finish at
around 3 pm today and try the second drive with a BS of 1M.
> /dev/urandom can be quite slow for large amounts.
OK. I'll try the second drive with zeros.
> One can go faster still by cutting out a read(2) for every write(2) by
> having a little Perl script or C program that loops, flinging the same
> data read once into every write().
Thanks. I think I'll keep it simple though :-)
> > It seems to be pretty quick having reached 22 GB done in around 40
> > minutes.
>
> I'm assuing that's GiB to the drive's TB.
>
> $ units -1v 22GiB/40minutes hour/TB
> reciprocal conversion
> 1 / (22GiB/40minutes) = 28.221896 hour/TB
> $
Yeah, see my other post relating to my arithmetic ;-(
--
Terry Coles
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