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

Peter Schuller wrote:
>> 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.

The meta data is kept at the end of the device; I always use the -h flag
 when labelling to get around this problem, as it records the name of
the "contained" device in the meta block and never gets confused that way.

Joe