gmirror and the UFS file systems

Mel fbsd.questions at
Fri Nov 28 09:30:05 PST 2008

On Friday 28 November 2008 18:08:19 Andrew Falanga wrote:

> I'm getting ready to move forward on enabling gmirror on my churches
> website server (FreeBSD 7.0-RELEASE p4).  I used defaults during the
> install (most importantly for this, the file system defaults).  I've read
> in the manual pages that the data for the mirror is contained in the last
> sector of the drive/partitions.  So, I want to mirror the entire drive
> (ad4) to the second drive (ad5).  This server doesn't yet have much data at
> all.  I'm wondering if I turn on this mirror, will anything important be
> overwritten in the last sector?

I've converted UFS filesystems with just the base install and a few ports over 
to gmirror many times and no problem.

I guess the question can best be paraphrased as:
"If I cross a street in a residential area at 4am in the morning, will I get 
hit by a car?"

Also, gmirror create will tell you if the last sector contains data, just like 
a driver would honk his horn.


Problem with today's modular software: they start with the modules
    and never get to the software part.

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