gemor mirror and priority

[Ulrich Spörlein]

On Sat, 21.03.2009 at 08:44:42 -1000, Clifton Royston wrote:
>   Even if you don't, I think it's quite useful to make the *default*
> priority set when creating a mirror be some value which allows both
> higher and lower values to be specified.  I hadn't known about that
> issue until I read the original thread here a while back.If the default
> were set to some mid-range value, or even to 2, for example, then at
> least creating a new mirror and adding drives without setting a
> priority would continue to behave as usual, while it would be possible
> to explicitly insert new components with a lower priority.  (I see why
> one wouldn't want to change the default interpretation of existing
> priority values for POLA reasons.)
> 
>   There are lots of reasons one could want to control priorities of
> mirrored drives in various ways.  One is to use gmirror as a long-term
> backup approach: mirror with three drives, periodically disconnecting
> one from the mirror to swap it with a fresh drive from a pool of backup
> drives.  I haven't tried this, but it's been on my mind to mess around
> with soon.

I did this for 2-3 years and it has worked very well. Of course I took
care of using the right priorities from the start. This setup has now
been replaced by a ZFS mirror. The resilver time is just so much better :)

>   In this case, I would want the designated backup drive to always be
> lowest-priority, to ensure the mirror never accidentally started
> rebuilding from a newly reinserted backup.  (This probably wouldn't
> happen anyway, but it would be nice to be sure...)

This will not happen. Besides, I would strongly encourage you to disable
automatic rebuilding for this type of setup.

Cheers,
Ulrich Spörlein
-- 
None are more hopelessly enslaved than those who falsely believe they are free
-- Johann Wolfgang von Goethe