ZFS attaching direct access drives as Scsibus#target#drive#

[Peter Schuller]

> glabel can have some funny effects due to the geom taste order.  If
> something is part of a mirror (for instance) and the label tastes before the
> mirror, I've seen items of the mirror come up with glabel instead of
> attaching to the mirror.

Does gmirror perhaps keep meta-data at the beginning of the underlying
device?

Something which can easily happen is that you have, for example, a
slice covering the entire device (exactly the entire device). You then
glabel the slice, and when you reboot the underlying device is labeled
instead of the slice. Similar issues can happen in other cases, such
as glabel:ing an iSCSI target on another host, if that iSCSI target is
backed by, for example, a zvol. 

For these reasons I always make sure that the "contained" device ends
earlier than the "containing" device (and the other way around). This
way there is never any GEOM (disk, slice, partition, glabel, gmirror,
etc) which starts or ends at the exact same spot as another GEOM. This
removes the ambiguity.

At least this is my interpretation of the situation; I haven't gone
and proven it.

-- 
/ Peter Schuller

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