5.4.16.8. Setting a RAID fault policy LVM RAID handles device failures in an automatic fashion based on the preferences defined by the raid_fault_policy field in the lvm.conf file. If the raid_fault_policy field is set to allocate , the system will attempt to replace the failed device with a spare device from the volume group. If there is no available spare device, this will be reported to the system log. If the raid_fault_policy field is set to warn , the system will produce a warning and the log will indicate that a device has failed. This allows the user to determine the course of action to take. As long as there are enough devices remaining to support usability, the RAID logical volume will continue to operate. 5.4.16.8.1. The allocate RAID Fault Policy In the following example, the raid_fault_policy field has been set to allocate in the lvm.conf file. The RAID logical volume is laid out as follows. If the /dev/sde device fails, the system log will display error messages. Since the raid_fault_policy field has been set to allocate , the failed device is replaced with a new device from the volume group. Note that even though the failed device has been replaced, the display still indicates that LVM could not find the failed device. This is because, although the failed device has been removed from the RAID logical volume, the failed device has not yet been removed from the volume group. To remove the failed device from the volume group, you can execute vgreduce --removemissing VG . If the raid_fault_policy has been set to allocate but there are no spare devices, the allocation will fail, leaving the logical volume as it is. If the allocation fails, you have the option of fixing the drive, then deactivating and activating the logical volume, as described in Section 5.4.16.8.2, "The warn RAID Fault Policy" . Alternately, you can replace the failed device, as described in Section 5.4.16.9, "Replacing a RAID device" .

Commands:
lvs -a -o name,copy_percent,devices my_vg LV Copy% Devices my_lv 100.00 my_lv_rimage_0(0),my_lv_rimage_1(0),my_lv_rimage_2(0) [my_lv_rimage_0] /dev/sde1(1) [my_lv_rimage_1] /dev/sdf1(1) [my_lv_rimage_2] /dev/sdg1(1) [my_lv_rmeta_0] /dev/sde1(0) [my_lv_rmeta_1] /dev/sdf1(0) [my_lv_rmeta_2] /dev/sdg1(0)
grep lvm /var/log/messages Jan 17 15:57:18 bp-01 lvm[8599]: Device #0 of raid1 array, my_vg-my_lv, has failed. Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at 250994294784: Input/output error Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at 250994376704: Input/output error Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at 0: Input/output error Jan 17 15:57:18 bp-01 lvm[8599]: /dev/sde1: read failed after 0 of 2048 at 4096: Input/output error Jan 17 15:57:19 bp-01 lvm[8599]: Couldn't find device with uuid 3lugiV-3eSP-AFAR-sdrP-H20O-wM2M-qdMANy. Jan 17 15:57:27 bp-01 lvm[8599]: raid1 array, my_vg-my_lv, is not in-sync. Jan 17 15:57:36 bp-01 lvm[8599]: raid1 array, my_vg-my_lv, is now in-sync.
lvs -a -o name,copy_percent,devices vg Couldn't find device with uuid 3lugiV-3eSP-AFAR-sdrP-H20O-wM2M-qdMANy. LV Copy% Devices lv 100.00 lv_rimage_0(0),lv_rimage_1(0),lv_rimage_2(0) [lv_rimage_0] /dev/sdh1(1) [lv_rimage_1] /dev/sdf1(1) [lv_rimage_2] /dev/sdg1(1) [lv_rmeta_0] /dev/sdh1(0) [lv_rmeta_1] /dev/sdf1(0) [lv_rmeta_2] /dev/sdg1(0)