Red Hat Enterprise Linux 5 Administration Unleashed

182CHAPTER 7Managing StorageIf a partition in the array fails, use the following to remove it from the array and rebuildthe array using the spare partition already added:mdadm /dev/mdX -f For example, to fail /dev/sda5 from /dev/md0 and replace it with the spare (assuming thespare has already been added):mdadm /dev/md0 -f /dev/sda5To verify that the device has been failed and that the rebuild has been complete and wassuccessful, monitor the /proc/mdstat file (output shown in Listing 7.9):tail -f /proc/mdstatNotice that /dev/sda5 is now failed and that /dev/sda8 has changed from a spare to anactive partition in the RAID array.LISTING 7.9Failing a Partition and Replacing with a SparePersonalities : [raid0] [raid1]md0 : active raid1 sda8[3] sda7[2] sda6[1] sda5[4](F)10241280 blocks [3/2] [_UU][>....................] recovery = 0.2% (30528/10241280) finish=11.1minspeed=15264K/secunused devices: Monitoring RAID DevicesThe following commands are useful for monitoring RAID devices:. cat /proc/mdstat: Shows the status of the RAID devices and the status of anyactions being performed on them such as adding a new member or rebuilding thearray.. mdadm --query /dev/mdX: Displays basic data about the device such as size andnumber of spares such as:/dev/md0: 9.77GiB raid1 3 devices, 1 spare.Add the --detail option to display more data ( mdadm --query --detail/dev/mdX):/dev/md0:Version : 00.90.03Creation Time : Mon Dec 18 07:39:05 2006Raid Level : raid1Array Size : 10241280 (9.77 GiB 10.49 GB)