gptboot: invalid backup GPT header

[John]

Hello lists,

Not sure if this is a hardware problem or a filesystem problem, so have 
cc'd to freebsd-fs@

The "problem" is on newly-installed freebsd 10.1 RC3. I say "problem" in 
inverted commas because it's not stopping it from booting and the server 
seems to run allright, I'm wondering if it's anything to worry about. As 
well as seeing gptboot: invalid backup GPT header *before* beastie 
starts, I see the following in dmesg:

GEOM: mfid1: corrupt or invalid GPT detected.
GEOM: mfid1: GPT rejected -- may not be recoverable.

There are 4 disks installed - mfid0,1,2 & 3. mfid0 is a regular ufs gpt 
based disk. mfid1,2 and 3 together form a zfs raidz array. A thread on 
https://forums.freenas.org/index.php?threads/gpt-table-is-corrupt-or-invalid-error-on-bootup.12171/
describes a similar problem - the thing is though the "erroring" disk is 
not a GPT disk, and the one in the example was.

# gpart list mfid1
gpart: No such geom: mfid1.

# ls -la /dev/mfid*
crw-r-----  1 root  operator  0x62 Nov  1 13:37 /dev/mfid0
crw-r-----  1 root  operator  0x66 Nov  1 13:37 /dev/mfid0p1
crw-r-----  1 root  operator  0x67 Nov  1 13:37 /dev/mfid0p2
crw-r-----  1 root  operator  0x68 Nov  1 13:37 /dev/mfid0p3
crw-r-----  1 root  operator  0x63 Nov  1 13:37 /dev/mfid1
crw-r-----  1 root  operator  0x64 Nov  1 13:37 /dev/mfid2
crw-r-----  1 root  operator  0x65 Nov  1 13:37 /dev/mfid3

# zpool status
  pool: vms
  state: ONLINE
  scan: none requested

config:

        NAME        STATE     READ WRITE CKSUM
        vms         ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            mfid1   ONLINE       0     0     0
            mfid2   ONLINE       0     0     0
            mfid3   ONLINE       0     0     0

errors: No known data errors

Should I worry?

-- 
John