fastest raw device copy?

[Jerry McAllister]

On Fri, Oct 31, 2008 at 04:48:32PM +0100, Christoph Kukulies wrote:

> Jerry McAllister schrieb:
> >On Fri, Oct 31, 2008 at 09:48:16AM +0100, Christoph Kukulies wrote:
> >
> >  
> >>Hi list,
> >>
> >>I'm considering using a bootable USB stick with FreeBSD to perform a 
> >>backup of my notebooks'
> >>500 GB hard disk to a physically identical (same make, same type, same 
> >>size) hard disk attached to  USB.
> >>
> >>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
> >>
> >>but maybe there is a utility which does this faster or a larger buffer 
> >>size? Probably the limit will be
> >>the USB 2.0 bus speed anyway?
> >>    
> >
> >Are you sure you want to do a sector-by-sector copy?
> >That won't get you much that is useful in terms of a backup.
> >
> >Can't you use dump/restore instead?
> >
> >Dump each file system on /dev/ad0 to a file on /dev/da0.
> >
> >Create a file system on /dev/da0 using newfs first.   You may or
> >may not want to create a FreeBSD slice and partition there before
> >doing the newfs.  
> >Make a mount point and mount it.
> >
> >mkdir /bkmnt
> >mount /dev/da0 /bkmnt    Or if you created slice and partition in /dev/da0
> >                         mount /dev/da0s1a /bkmnt
> >
> >Then do the dumps
> >
> >  dump 0af /bkmnt/rootbackup /
> >  dump 0af /bkmnt/usrbackup /usr
> >  dump 0af /bkmnt/homehackup /home
> >
> >etc for whatever file systems you want to back up.
> >
> >You will be much better off than with a sector by sector copy.
> >
> >////jerry
> >  
> 
> The idea was  to have a drop in backup for my notebook that allows me to 
> continue working with a minimum of delay. (requires a philips 
> screwdriver though :-)
> 
> Of course a failure of the source disk while doing the image copy as the 
> worst case scenario
> would leave me with empty hands :-)
> 
> There are a couple of partitions with different OSs on that hard drive.

Still, that is not really the best way to do backups.

For the FreeBSD, you can build the slice and partitions in it
and back up each appropriately.

Make mount points as needed
  mkdir /bkroot
  mkdir /bkusr
  mkdir /bkhome
etc
Do the mounts
  mount /dev/da0s1a /bkroot
  mount /dev/da0s1d /bkusr
  mount /dev/da0s1g /bkhome
etc  as appropriate
Make sure those filesystems on the USB are empty.
Then use dump/retore to make the copies

  cd /bkroot
  dump 0af - / | restore -rf -
  cd /bkusr
  dump 0af - /usr | restore -rf -
  cd /bkhome
  dump 0af - /home | restore -rf -
etc   as appropriate

This makes a much more reliable backup that the sector by sector thing.
If you make the slice bootable and have an MBR, it can be bootable.
It takes care of any difference in device size/block counts and dealing
with back blocks transparently.
  
If you have more than one slice and each has a different OS, then you 
need to make an equivalent backup for each OS to the appropriate slice 
on the USB.  

////jerry

> 
> --
> Christoph
> 
> 
> 
> _______________________________________________
> freebsd-questions at freebsd.org mailing list
> http://lists.freebsd.org/mailman/listinfo/freebsd-questions
> To unsubscribe, send any mail to "freebsd-questions-unsubscribe at freebsd.org"