On Jul 21, 2010, at 11:05 PM, Dan Langille wrote:
> I hope my terminology is correct....
>
> I have a ZFS array which uses raw devices. I'd rather it use glabel and
> supply the GEOM devices to ZFS instead. In addition, I'll also partition the
> HDD to avoid using the entire HDD: leave a little bit of space at the start
> and end.
>
> Why use glabel?
>
> * So ZFS can find and use the correct HDD should the HDD device ever
> get renumbered for whatever reason. e.g. /dev/da0 becomes /dev/da6
> when you move it to another controller.
I have created ZFS pools using this strategy. However, about a year ago I
still fell foul of the drive shuffling problem, when GEOM labels appeared not
to be detected properly:
http://lists.freebsd.org/pipermail/freebsd-geom/2009-July/003654.html
This was using RELENG_7, and the problem was provoked by external USB drives.
The same issue might not occur with FreeBSD 8.x, but I thought I'd point out my
experience as a possible warning about using glabel.
Nowadays, I use GPT labels ("gpart ... -l somelabel", referenced via
/dev/gpt/somelabel).
> Why use partitions?
>
> * Primarily: two HDD of a given size, say 2TB, do not always provide
> the same amount of available space. If you use a slightly smaller
> partition instead of the entire physical HDD, you're much more
> likely to have a happier experience when it comes time to replace an
> HDD.
>
> * There seems to be a consensus amongst some that leaving the start and
> and of your HDD empty. Give the rest to ZFS.
You should also try and accommodate 4K sector size drives these days.
Apparently, the performance boosts from hitting 4K-aligned sectors can be very
good.
Cheers,
Paul._______________________________________________
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