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I have a raid6 array with 5 disks(was started with 4 and then added on on-the fly - without rebooting). I have noticed something a bit strange when i was preparing to add a new drive :

mdadm --examine --scan gives 4 UUIDS ARRAY /dev/md/99 metadata=1.2 UUID=e23feeb5:a75b13a4:cab78db9:b213b746 while mdadm --detail /dev/md99 lists 5 drives (but still 4 UUIDs)

Creation Time : Fri May 17 11:53:09 2013 Raid Level : raid6 Array Size : 8790405120 (8383.18 GiB 9001.37 GB) Used Dev Size : 2930135040 (2794.39 GiB 3000.46 GB) Raid Devices : 5 Total Devices : 5 Persistence : Superblock is persistent

Update Time : Sun Aug  4 09:24:27 2013
      State : active

Active Devices : 5 Working Devices : 5 Failed Devices : 0 Spare Devices : 0

     Layout : left-symmetric
 Chunk Size : 512K

       UUID : e23feeb5:a75b13a4:cab78db9:b213b746
     Events : 5251

Question:why 4 UUIDs when there are 5 drives?I would like to update mdadm.conf but can't get that 5'th UUID. Am i safe?

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