freebsd stable - Jun 2007 - gmirror on a disk with data already on it

Hiho! :-)

The gmirror man page says that if gmirror is used on a disk, the last
sector of that disk is overwritten with the metadata gmirror uses.

So what I would like to know is, how risky is it to mirror a disk which
already has data on it?

Is there a chance that I might render my system unbootable?

Is there any way to find out what data that last sector holds?

Thanks in advance! :-)

Bye
Marc

Marc UBM Bocklet <ubm@u-boot-man.de> wrote:
 > The gmirror man page says that if gmirror is used on a disk, the last
 > sector of that disk is overwritten with the metadata gmirror uses.
 > 
 > So what I would like to know is, how risky is it to mirror a disk which
 > already has data on it?
 > 
 > Is there a chance that I might render my system unbootable?

If you follow the procedure in the Handbook, then there is
no risk at all.  It involves preparing one side of the
mirror on the second (unused) device first, then attaching
the first device to the mirror.

Best regards
   Oliver

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