Ok. Assume for starters that the disk is Ok (doing the same mistake twice). Then try to rebuild the array with the filesystem alive as follows:

• Use 3dm2 to (a) remove the drive from the unit,
• Rescan the card to make the drive available again,
• Start rebuilding the array at low priority → see how it goes

Even if that works, a reboot appears to be unavoidable: no error messages were e-mailed or logged for the array degradation or that the rebuild started.

Hate it:

 	Port 0  WDC WD5002ABYS-01B1B0  	465.76 GB  	OK  	 
	Port 1 	WDC WD5002ABYS-02B1B0 	465.76 GB 	OK 	 
	Port 2 	WDC WD5002ABYS-01B1B0 	465.76 GB 	OK 	 
	Port 3 	WDC WD5002ABYS-01B1B0 	465.76 GB 	DEGRADED 	[Remove Drive]

corresponding to

0  	WDC WD5002ABYS-01B1B0  	465.76 GB  	WD-WCASY2089577  	02.03B02  	0  	OK  	
1 	WDC WD5002ABYS-02B1B0 	465.76 GB 	WD-WCASY6818600 	02.03B03 	0 	OK 	
2 	WDC WD5002ABYS-01B1B0 	465.76 GB 	WD-WCASY2078275 	02.03B02 	0 	OK 	
3 	WDC WD5002ABYS-01B1B0 	465.76 GB 	WD-WCASY2161066 	02.03B02 	0 	OK