gmirror existing installation?

[R. B. Riddick]

Oliver Fromme <olli at lurza.secnetix.de> wrote: Mike Jakubik wrote:
> > I don't recommend to do it that way.  It is better to first
> 
 > Exactly why is this better?

Because you don't overwrite the last sector of a partition
that contains an existing file system.  Overwriting that
sector might cause trouble depending on the layout of the
file system.

I think, he planned to re-bsdlabel that partition, which is possible, since sysinstall often leaves some sectors unused, because it believes it knows disk geometry...

Furthermore a UFS does not use the last sector, if(? and only(?) if(?) the size of the partition is an integer multiple of 4...

bsdlabel requires no service interruption (un-mount or so), if u want to enlarge a partition...
> It's certainly much more time consuming...

Not really much more.  It's true that you have to copy over
your files, but the computer does all that work itself.
You only have to type one command, then spend your time
doing something else.  You don't have to watch it during
the copying.  (You don't have to watch the mirror being
synchronized either, which has to be done anyhow and takes
much longer, probably.)

The service interruption is higher, because copying the system should be done with a read-only root-fs...

Both methods need a reboot in order to change the root fs...

So the method proposed intially in this thread is only feasible under certain circumstances, and involves nearly zero down time (if and only if the quite high disk load is tolerated by the services).

It is always better to design the system before it is installed... :-)

-Arne

 
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