'gpart show' Two devices for an external disk?

[jaymax]

Is it normal that
gpart show
shows 2 devices for an external disk ? this question was asked by Thierry Leloup in Thread failed-to-add-external-hard-disk-with-freebsd-10-1.52024/ below. I have a similar problem with an external hard disk hanging on a usb adapter. Shown as da0 and its diskid below.

gpart show ==>

=> 
  34                  976773101            ada1  GPT  (466G)
  34                            1024                  1  freebsd-boot  (512K)
  1058              968883200                  2  freebsd-ufs  (462G)
  968884258        7888876                  3  freebsd-swap  (3.8G)
  976773134                    1  - free -  (512B)

=>  34             781422701            ada2  GPT  (373G)
  34                             128                  1  freebsd-boot  (64K)
  162               773848960                  2  freebsd-ufs  (369G)
  773849122        7573612                 3  freebsd-swap  (3.6G)
  781422734                    1  - free -  (512B)

=>  34             312581741              da0  GPT  (149G)
       34             312581741                  1  freebsd-ufs  (149G)

=>  34             312581741               diskid/DISK-20140919  GPT  (149G)
  34                  312581741              1  freebsd-ufs  (149G)

Not withstanding the resultant

# ls -aqxFl /usb_01

ls: /usb_01: Input/output error

Although this could spring from another source - running smartctl =>

# smartctl /dev/da0 =>
a NOW under FAIL in the Reallocated_Sector_Ct

Any clarification would be helpful and appreciated.

 

[wblock@]

These are several different issues. The diskid thing showing in addition to the expected one is normal. That can be disabled, although it's not a problem and can be ignored. An I/O error on a mount point is not related, and neither are bad sectors. Those should be asked about in separate threads.