[SunHELP] using dd

Lee Khuong sunhelp at sunhelp.org
Tue Feb 6 13:55:33 CST 2001


You need to specify the block size for the input and output file.  The
default block size is only 512, it will take forever to get your backup
done.  Try this.

# dd if=/dev/rdsk/c0t10d0s0 of=/dev/rdsk/c0t11d0s0 bs=1024k

However, with a filesystem that has only 1.5gb of data, it's much better
to go with a tar than a dd on a 17gb filesystem as Jeff Howie thought.


Jeff Howie wrote:
> Edward Chase wrote:
> > I'm working on developing a backup script for a Solaris 2.7 box.
> >
> > The machine has 2 internal 18GB hard drives.  (c0d10t0 and c0d11t0)
> >
> > I am using the dd command for the first time in hopes for a little
> > reduncancy and backup speed.  Here's my thoughts...
> >
> > Both drives are partitioned the same.  Right now, I've issued the following
> > command:
> >
> >     dd if=/dev/rdsk/c0t10d0s0 of=/dev/rdsk/c0t11d0s0
> >
> > I was thinking that this would create a quick snapshot of one filesystem
> > from one drive to the other and then I was going to run ufsdump from the
> > 2nd drive.  It's the / filesystem if that matters.
> >
> > I issued that command over an hour ago and it still appears to be
> > running.  The partition is 17GB or so, but only has 1.5GB of data in it.
> >
> > Should this be taking this long?  This machine is a 4 CPU - E4500 w/ 1GB of
> > RAM.  Only the basic OS is running at the moment.
> If I understand dd properly, you are now making a backup of a 17gb
> image, _NOT_ just the data on the drive! That might explain why it's
> taking so long :#>.
> We'll have to wait for backup experts to answer for what the best
> solution would be, I would suspect something along the lines of a simple
> tar command would serve you better.
> --
> thks
> jeff
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