Re: Some External HDD Questions

From: Jorge Delacruz <alterthegrid@yahoo.com>
> Matt Graham <danceswithcrows@usa.net> wrote:
> > 2M/s? That doesn't sound right for either USB1 or USB2.
> I plugged in a USB drive and [dd'ed] the internal drive to
> a file on the external USB drive. It took 9 hours to dd a
> 40 GB internal drive, so 1.2 MB/sec

What did you specify for bs= ? 32k or 64k would have probably
worked the best. If you don't specify a bs= , dd reads and
writes 512-byte blocks. This is ... suboptimal, as 64 reads of
0.5K take much longer than 1 read of 32K.

> I used USB2 hardware. Maybe this is a limitation with dd?
> The external hard drive's light blinks a lot and the box
> seems I/O bound when I do it.

Of course it's going to be I/O bound; you're doing a whole
bunch of I/O. See above for a possible explanation. Also,
dd is the stupidest backup method in existence as it copies
everything including blocks that aren't in use. Use partimage
or tar or rsync; that's what they're there for.


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