How to Replace a RAID5 Slice (Command Line)

This task replaces an errored slice of a RAID5 metadevice in which only one slice is errored.

Replacing an errored slice when multiple slices are in error may cause data to be fabricated. The integrity of the data in this instance is questionable.

After checking the prerequisites ("Prerequisites for Maintaining DiskSuite Objects"), the overview ("Overview of Replacing and Enabling Slices in Mirrors and RAID5 Metadevices"), and the preliminary information ("Preliminary Information For Replacing and Enabling Slices in Mirrors and RAID5 Metadevices"), follow this example to replace an errored slice in a RAID5 metadevice. Refer to the metareplace(1M) man page for more information.

Example -- Replacing a RAID5 Slice

# metastat d1
d1: RAID
State: Needs Maintenance
    Invoke: metareplace d1 c0t14d0s6 <new device>
    Interlace: 32 blocks
    Size: 8087040 blocks
Original device:
    Size: 8087520 blocks
	Device              Start Block  Dbase State        Hot Spare
	c0t9d0s6                 330     No    Okay        
	c0t13d0s6                330     No    Okay        
	c0t10d0s6                330     No    Okay        
	c0t11d0s6                330     No    Okay        
	c0t12d0s6                330     No    Okay        
	c0t14d0s6                330     No    Maintenance
 
# metareplace d1 c0t14d0s6 c0t4d0s6
d1: device c0t14d0s6 is replaced with c0t4d0s6
# metatstat d1
d1: RAID
    State: Resyncing
    Resync in progress: 98% done
    Interlace: 32 blocks
    Size: 8087040 blocks
Original device:
    Size: 8087520 blocks
	Device              Start Block  Dbase State        Hot Spare
	c0t9d0s6                 330     No    Okay        
	c0t13d0s6                330     No    Okay        
	c0t10d0s6                330     No    Okay        
	c0t11d0s6                330     No    Okay        
	c0t12d0s6                330     No    Okay
	c0t4d0s6                 330     No    Resyncing

The metastat command displays the action to take to recover from the errored slice in the d1 RAID5 metadevice. After locating an available slice, the metareplace command is run, specifying the errored slice first, then the replacement slice. (If no other slices are available, run the metareplace(1M) command with the -e option to attempt to recover from possible soft errors by resyncing the errored device.) If multiple errors exist, the slice in the "Maintenance" state must first be replaced or enabled first. Then the slice in the "Last Erred" state can be repaired. After the metareplace, metastat monitors the progress of the resync. During the replacement, the state of the metadevice and the new slice will be "Resyncing." You can continue to use the metadevice while it is in this state.

You can use the metareplace(1M) command on non-errored devices to change a disk (slice). This can be useful for tuning performance of RAID5 metadevices.