mdadm –manage /dev/md0 –add /dev/sdd1
mdadm: Cannot open /dev/sdd1: Device or resource busy
It means the disk is not new, it has data , it has some raid signature (raid metadata). reboot and try to insert in single user mode by using the below commands.
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mdadm –fail /dev/md0 /dev/sdd1
Even if the first command failed, run the below command.
mdadm –manage /dev/md0 –add /dev/sdd1
/dev/sdd1 added ==> the result should like this.
Now the result should be
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# cat /proc/mdstat
Personalities : [raid10] [raid1]
md0 : active raid1 sdd1[4] sdc1[1] sdb1[2] sda1[0]
200704 blocks [4/3] [UUU_]
resync=DELAYED
md3 : active raid10 sdd2[4] sdc2[1] sdb2[2] sda2[0]
1841964544 blocks 256K chunks 2 near-copies [4/3] [UUU_]
[========>…………] recovery = 41.5% (382455104/920982272) finish=148.3min speed=60480K/sec
md2 : active raid10 sdd5[3] sdc5[1] sdb5[2] sda5[0]
2104320 blocks 256K chunks 2 near-copies [4/4] [UUUU]
md1 : active raid10 sdd3[4] sdc3[1] sdb3[2] sda3[0]
109048832 blocks 256K chunks 2 near-copies [4/3] [UUU_]
resync=DELAYED
unused devices: <none>
===============
After resyncing the final result should be
md3 : active raid10 sdd2[4] sdc2[1] sdb2[2] sda2[0]
1841964544 blocks 256K chunks 2 near-copies [4/3] [UUUU]
catysweb 