The data are migrated into {HEAD ~ RAID 5 configurations} as {TAIL ~ a background operation}, to minimize the disk space lost 
The data are migrated into { HEAD ~ RAID 5 configurations } as { TAIL ~ a background operation } , to minimize the disk space lost
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH