Safe to ignore GEOM warnings on ZFS raidz?

[Clayton Fuller]

I am setting up a new home file server on CURRENT-8.0 using 4 1.5 TB  
SATA drives in a ZFS raidz pool
I created the pool without first partitioning or labeling the drives.

during the boot sequence, I get the following warnings for each of the  
drives:
GEOM: ad6: corrupt or invalid GPT detected.
GEOM: ad6: GPT rejected -- may not be recoverable.

here's the drive info (I have 3 identical drives at ad8, ad12 and ad14)
ad6: 1430799MB <Seagate ST31500341AS CC1H> at ata3-master SATA300

The storage pool seems to work fine, as tested by transferring nearly  
a terabyte of data, simulating a failed drive, resilvering, etc and  
all seems to be working well.

invoking the zpool scrub <poolname> command will bring up the corrupt  
GPT errors again, but all other read/write operations on my storage  
pool seem to be fine.

Is GEOM in any way necessary for managing this ZFS pool? Can I safely  
ignore the warnings? Is there a better way to configure this to keep  
GEOM happy?

I'd be happy to supply more specifics if germane, but thought I'd try  
to keep it simple.

Any suggestions would be greatly appreciated.

-Clayton