ZFS With Gpart partitions

[Dan Carroll]

Hello all,

I'm currently trying to fix a suspect drive and I've run into a small 
problem.
I was wondering if someone can shed some light into how GPart works 
(when using labels for partitions).

My drives are 2Tb WD RE4's, originally the array was using 1Tb Seagate 
drives, and I was replacing about 3 of those a year, but since I 
migrated to the RE4's this is my first problem.
Here is my setup.

         NAME                 STATE     READ WRITE CKSUM
         areca                ONLINE       0     0     0
           raidz1             ONLINE       0     0     0
             gpt/data0        ONLINE       0     0     0
             gpt/data1        ONLINE       0     0     0
             gpt/data2        ONLINE       0     0     0
             gpt/data3        ONLINE       103   0     0
             gpt/data4        ONLINE       0     0     0
             gpt/data5        ONLINE       0     0     0
           raidz1             ONLINE       0     0     0
             gpt/data6        ONLINE       0     0     0
             gpt/data7        ONLINE       0     0     0
             gpt/data8        ONLINE       0     0     0
             gpt/data9        ONLINE       0     0     0
             gpt/data10       ONLINE       0     0     0
             gpt/data11       ONLINE       0     0     0

errors: No known data errors

The drives are connected via an Areca controller, each drive is created 
as a Pass-Thru (just like JBod but also using the cache and BBU).
So, my problem began when I tried to replace gpt/data3.

Here is what I did.

# zpool offline areca gpt/data3
# shutdown -p now

(I could not remember the camcontrol commands to detach a device and 
shutting down was not an issue, so that's the way I did it.)
Replace the failing drive and re-create the passthru device in the areca 
console.
power on.

All good so far, except the drive I used as a replacement came from a 
decomissioned server.  It already had a gpart label on it.
As it happens it was labelled data2.

I quickly shut down the system, took the new drive out, put it into 
another machine and wiped the first few megabytes of the disk with dd.

I re-inserted the drive, recreated the passthrough, powered up and 
replaced the offlined drive.
Now it's resilvering.
Currently, my system looks like this:

         NAME                 STATE     READ WRITE CKSUM
         areca                DEGRADED     0     0     0
           raidz1             DEGRADED     0     0     0
             gpt/data0        ONLINE       0     0     0
             gpt/data1        ONLINE       0     0     0
             da8p1            ONLINE       0     0     0
             replacing        DEGRADED     0     0     0
               gpt/data3/old  OFFLINE      0     0     0
               gpt/data3      ONLINE       0     0     0  931G resilvered
             gpt/data4        ONLINE       0     0     0
             gpt/data5        ONLINE       0     0     0
           raidz1             ONLINE       0     0     0
             gpt/data6        ONLINE       0     0     0
             gpt/data7        ONLINE       0     0     0
             gpt/data8        ONLINE       0     0     0
             gpt/data9        ONLINE       0     0     0
             gpt/data10       ONLINE       0     0     0
             gpt/data11       ONLINE       0     0     0

The resilvering looks like it's working fine, but I am curious about the 
gpart label.   When I query da8p1 I cannot find it.
# gpart show da8
=>        34  3907029101  da8  GPT  (1.8T)
           34  3907029101    1  freebsd-zfs  (1.8T)

# glabel list da8p1
glabel: No such geom: da8p1.

It should look like this:

# gpart show da0
=>        34  3907029101  da0  GPT  (1.8T)
           34  3907029101    1  freebsd-zfs  (1.8T)

# glabel list da0p1
Geom name: da0p1
Providers:
1. Name: gpt/data0
    Mediasize: 2000398899712 (1.8T)
    Sectorsize: 512
    Mode: r1w1e1
    secoffset: 0
    offset: 0
    seclength: 3907029101
    length: 2000398899712
    index: 0
Consumers:
1. Name: da0p1
    Mediasize: 2000398899712 (1.8T)
    Sectorsize: 512
    Mode: r1w1e2


So it seems to me that when I inserted the second drive with a label 
called data2, it wiped the label from the *original* drive.
ZFS does not seem to care about this.  If the label is simply a label 
and losing it does not alter the user data on the drive, then this makes 
sense.

I am wondering if I can simply re-label the partition without fear of 
breaking something?  Reading the glabel man page I suspect that it may 
be ok.

-D