Newbie gmirror questions

Mike Clarke jmc-freebsd2 at
Sun Jan 17 21:22:17 UTC 2010

On Sunday 17 January 2010, Matthew Seaman wrote:

> Mike Clarke wrote:
> > Actually I was more concerned about what happens when I boot into
> > another OS like Windows or Linux on one of the spare slices - I'm
> > assuming that I have to apply gmirror to the whole disk rather than
> > just selected slices?
> You can't do this.  gmirror is FreeBSD specific, and other OSes can't
> deal with it.  You can take your two drives, partition them (fdisk)
> and then create a gmirror across the slices you assign to FreeBSD.

This will make things a lot easier for me. I think all the examples of 
gmirror I've seen used things like /dev/da0 as the provider in label 
commands so I assumed that I had to use the whole physical disk but if 
I can mirror individual slices then I have much more flexibility.

My motherboard has a UDMA133 controller for ata0 & ata1 (which I don't 
use) and 2 SATA controllers for ata2 to ata5 so with my 2 SATA drives 
spread between the controllers on channels 2 & 4 I could have something 
like /dev/mirror/gm1 provided by /dev/ad2s1 & /dev/ad4s1 
and /dev/mirror/gm2 provided by /dev/ad2s2 & /dev/ad4s2 for a couple of 
FreeBSD systems. That will leave me with 2 spare slices on each drive 
for other purposes. Any Windows or Linux stuff I put on tends to be 
mainly experimental and less long term than my FreeBSD system so don't 
really need the resilience of being mirrored.

Mike Clarke

More information about the freebsd-questions mailing list