This is a FreeBSD 9.1 amd64 computer. It has 5 disks installed. The ada0 and ada1 disks are used with a hw raid to provide the root filesystem:

root@gw:/home/gandalf # ls /dev | grep ada
ada0
ada1
ada2
ada3
ada4
root@gw:/home/gandalf # zpool status
  pool: zroot
 state: ONLINE
  scan: none requested
config:

    NAME          STATE     READ WRITE CKSUM
    zroot         ONLINE       0     0     0
      raid/r0s1a  ONLINE       0     0     0

errors: No known data errors

I want to create a raidz pool for the remaining disks:

root@gw:/home/gandalf # zpool create -f data raidz1 ada2 ada3 ada4
cannot create 'data': one or more devices is currently unavailable
root@gw:/home/gandalf # dmesg | grep ada2
ada2 at ata4 bus 0 scbus6 target 0 lun 0
ada2: <WDC WD20EARS-00MVWB0 51.0AB51> ATA-8 SATA 2.x device
ada2: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes)
ada2: 1907729MB (3907029168 512 byte sectors: 16H 63S/T 16383C)
ada2: Previously was known as ad16
root@gw:/home/gandalf # dmesg | grep ada3
ada3 at ata5 bus 0 scbus7 target 0 lun 0
ada3: <SAMSUNG HD103UJ 1AA01118> ATA-7 SATA 2.x device
ada3: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes)
ada3: 953868MB (1953523055 512 byte sectors: 16H 63S/T 16383C)
ada3: Previously was known as ad18
GEOM_RAID: Intel-fb8732fa: Disk ada3 state changed from NONE to ACTIVE.
GEOM_RAID: Intel-fb8732fa: Subdisk Volume0:0-ada3 state changed from NONE to ACTIVE.
root@gw:/home/gandalf # dmesg | grep ada4
ada4 at ata6 bus 0 scbus8 target 0 lun 0
ada4: <TOSHIBA DT01ACA100 MS2OA750> ATA-8 SATA 3.x device
ada4: 300.000MB/s transfers (SATA 2.x, UDMA5, PIO 8192bytes)
ada4: 953869MB (1953525168 512 byte sectors: 16H 63S/T 16383C)
ada4: Previously was known as ad20
root@gw:/home/gandalf # dmesg | grep GEOM_RAID

Aha, so ada3 is already part of another raid volume? Let's see:

root@gw:/home/gandalf # dmesg | grep GEOM_RAID
GEOM_RAID: SiI-130628113902: Array SiI-130628113902 created.
GEOM_RAID: SiI-130628113902: Disk ada0 state changed from NONE to ACTIVE.
GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:1-ada0 state changed from NONE to STALE.
GEOM_RAID: SiI-130628113902: Disk ada1 state changed from NONE to ACTIVE.
GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:0-ada1 state changed from NONE to STALE.
GEOM_RAID: SiI-130628113902: Array started.
GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:0-ada1 state changed from STALE to ACTIVE.
GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:1-ada0 state changed from STALE to RESYNC.
GEOM_RAID: SiI-130628113902: Subdisk SiI Raid1 Set:1-ada0 rebuild start at 0.
GEOM_RAID: SiI-130628113902: Volume SiI Raid1 Set state changed from STARTING to SUBOPTIMAL.
GEOM_RAID: SiI-130628113902: Provider raid/r0 for volume SiI Raid1 Set created.
GEOM_RAID: Intel-fb8732fa: Array Intel-fb8732fa created.
GEOM_RAID: Intel-fb8732fa: Force array start due to timeout.
GEOM_RAID: Intel-fb8732fa: Disk ada3 state changed from NONE to ACTIVE.
GEOM_RAID: Intel-fb8732fa: Subdisk Volume0:0-ada3 state changed from NONE to ACTIVE.
GEOM_RAID: Intel-fb8732fa: Array started.
GEOM_RAID: Intel-fb8732fa: Volume Volume0 state changed from STARTING to DEGRADED.
GEOM_RAID: Intel-fb8732fa: Provider raid/r1 for volume Volume0 created.
root@gw:/home/gandalf # 

Yes, indeed. I want to get rid of raid/r1 completely. However, the controller was already set to "IDE" mode in the BIOS. So why it is creating a raid volume??? I have also tried overwritting the first 16k data of ada3 and reboot the computer, but it did not help.

How can I delete /dev/raid/r1 ?

root@gw:/home/gandalf # graid status
   Name      Status  Components
raid/r0  SUBOPTIMAL  ada0 (ACTIVE (RESYNC 4%))
                     ada1 (ACTIVE (ACTIVE))
raid/r1    DEGRADED  ada3 (ACTIVE (ACTIVE))
root@gw:/home/gandalf # graid delete raid/r1
graid: Array 'raid/r1' not found.
root@gw:/home/gandalf # graid delete /dev/raid/r1
graid: Array '/dev/raid/r1' not found.
root@gw:/home/gandalf #

Thanks