Basic Command List
- gmirror status
- Lists the current status of all gmirrors on the system.
- gmirror list
- Prints detailed information about the devices within a mirror.
- gmirror remove <mirror> <device>
- Removes <device> from <mirror>. This is the clean and preferred method.
- gmirror forget <mirror>
- Causes missing devices to be dropped from a mirror.
- This is useful when you need to replace a drive that has failed.
- gmirror insert <mirror> <device>
- Inserts <device> into <mirror>.
- This method assumes you already have FreeBSD installed on the first drive. Many of these steps are not necessary if your mirror is not going to be your boot device.
- Boot system from a FreeBSD 5.4+ Install CD (full disc, not boot-only)
- After the installer starts, select Fixit, and From CD/DVD
- When the Fixit prompt appears, run the following commands:
Fixit# chroot /dist Fixit# mount_devfs devfs /dev
- Run the following command for each of the disks in your new array, where <device_name> is the name of the device as listed in /dev:
Fixit# gmirror clear /dev/<device_name>
- Load the gmirror kernel module:
Fixit# gmirror load
- Create and Initialize the mirror:
Fixit# gmirror label -v -b load gm0 /dev/<device_name> Fixit# mount /dev/mirror/gm0s1a /mnt
- Edit /boot/loader.conf to load the geom_mirror kernel module at boot:
Fixit# echo geom_mirror_load=\"YES\" >> /mnt/boot/loader.conf
- Edit /etc/rc.conf to turn off system swap. Swap will be handled automatically by geom:
Fixit# echo swapoff=\"YES\" >> /mnt/etc/rc.conf
- Edit fstab to point to /dev/mirror/gm0xxx either manually, or with sed command here:
Fixit# sed -i ".bak" "s%ad0%mirror/gm0%g" /mnt/etc/fstabb
- Note that the sed command above assumes your current boot device is ad0, change this value accordingly for your system.
- Reboot your system!
Fixit# shutdown -r now
- Once the system has rebooted, insert the other device into your mirror with the following command, where <device_2_name> is the name in /dev of your second device:
Fixit# gmirror insert gm0 /dev/<device_2_name>
Inevitably, there will come a time when we need to rebuild an array due to hard disk failure or some other mean nasty. Follow the steps below, and you'll be on your way to a COMPLETE status once again.
- First off, remove the offending device if you haven't already done so. Upon removal, you should see some messages indicating the loss of a device. Something like:
(da1:ahc0:0:1:0): lost device (da1:ahc0:0:1:0): Invalidating pack GEOM_MIRROR: Cannot write metadata on da1 (device=gm0, error=6). GEOM_MIRROR: Cannot update metadata on disk da1 (error=6). GEOM_MIRROR: Device gm0: provider da1 disconnected. (da1:ahc0:0:1:0): Synchronize cache failed, status == 0x4a, scsi status == 0x0 (da1:ahc0:0:1:0): removing device entry
You'll also notice that the device entry has disappeared from /dev.
- Once the disk has been removed, replace it with a shiny new(ish) drive.
- Reread the SCSI or ATA bus with the appropriate command:
- SCSI (where 0 is the bus_id):
# camcontrol rescan 0
- ATA (where 0 is the bus_id):
# atacontrol attach 0
da1 at ahc0 bus 0 target 1 lun 0 da1: <SEAGATE ST318305LC 2202> Fixed Direct Access SCSI-3 device da1: 160.000MB/s transfers (80.000MHz, offset 63, 16bit), Tagged Queueing Enabled da1: 17366MB (35566478 512 byte sectors: 255H 63S/T 2213C)
- SCSI (where 0 is the bus_id):
- Tell gmirror to forget about the missing drive, so we can insert the new one.
# gmirror forget gm0
- Insert the new disk into the mirror where <new_device> is the full path to the new device (ex /dev/da1):
# gmirror insert gm0 <new_device>
If the above command is successful, you'll see a message similar to:
GEOM_MIRROR: Device gm0: provider da1 detected. GEOM_MIRROR: Device gm0: rebuilding provider da1.
- Check the status of the rebuild with gmirror status command:
gmirror status Name Status Components mirror/gm0 DEGRADED da0 da1 (48%)