gmirror confusion

Ken Gunderson kgunders at teamcool.net
Fri Dec 10 18:25:27 PST 2004


Hello:

Been fighting gmirror for longer than I want to admit and going to have 
to break down and ask for help on what at first blush seems should be 
trivial...  Would somebody please elaborate upon Pawel's post in the 
gmirror problmes thread:

<pjb>
The safest way to do what you want is to:

        # gmirror label <name> ad1
        create slices and partitions on /dev/mirror/<name>
        create file system
        copy data from ad0 to <name>
        change /etc/fstab to boot from /dev/mirror/<name>s1a or 
something
        reboot
        # gmirror insert <name> ad0
</pjb>

I have two disks, ad0 and ad2 that I'd like to mirror.  In the past  
would have just bootstrapped vinum.  Gmirror seems like a better way to 
go for this type of application but I'm only recently using 5.3 on 
production machines so haven't had the chance to become as familiar 
with geom as I probably should be.  

I can get the mirror configured with the live files system trick, but 
not the above, which Pawel mentions as the "safest" way to handle this.

For example, I've searched archives and seen references to both

1) "create slices and partitions on /dev/mirror/<name>"

as well as

2) "create slices and partitions on provider"

As well as confusion about whether the mirror's label should have the 16 
sector offset thrown at it by bsdlabel, or whether I should just clone 
the label from the drive I did the install on.

I'm also curious whether anyone has done any performance testing of the 
different balance options.  For booting from 2 mirrored drives, I 
assume either "load" or "round-robin" would be the options of choice?

TIA--

-- 
Best regards,

Ken Gunderson
GPG Key-- 9F5179FD

"Freedom begins between the ears."      -- Edward Abbey


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