Question How to add removed disk to RAID1 ?

[pcu123]

I have an old NAS called Netgear Stora. It has two SSD drives in RAID1. Unfortunately one of the drives started to light red on the cover and it appeared that it is removed from the array:

-bash-3.2$ sudo mdadm --detail /dev/md0
/dev/md0:
Version : 01.00.03
Creation Time : Mon Feb 9 21:34:51 2015
Raid Level : raid1
Array Size : 2930266412 (2794.52 GiB 3000.59 GB)
Used Dev Size : 5860532824
Raid Devices : 2
Total Devices : 1
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Sun Jan 7 14:55:42 2024
State : clean, degraded
Active Devices : 1
Working Devices : 1
Failed Devices : 0
Spare Devices : 0

Name : 0
UUID : 08b6f7f1:b7f81bac:754a1ac8:b18cb525
Events : 66838

Number Major Minor RaidDevice State
0 8 1 0 active sync /dev/sda1
1 0 0 1 removed

When I try to add the disk I get:

-bash-3.2$ sudo mdadm --manage /dev/md0 --add /dev/sdb1
mdadm: /dev/sdb1 not large enough to join array

Why do I get this? The drives are identical:

-bash-3.2$ sudo mdadm --examine /dev/sda1
/dev/sda1:
Magic : a92b4efc
Version : 1.0
Feature Map : 0x0
Array UUID : 08b6f7f1:b7f81bac:754a1ac8:b18cb525
Name : 0
Creation Time : Mon Feb 9 21:34:51 2015
Raid Level : raid1
Raid Devices : 2

Avail Dev Size : 5860532824 (2794.52 GiB 3000.59 GB)
Array Size : 5860532824 (2794.52 GiB 3000.59 GB)
Super Offset : 5860533080 sectors
State : clean
Device UUID : 29ecae47:9408fb85:f7e85ced:4ed7c3e7

Update Time : Sun Jan 7 14:52:40 2024
Checksum : aa3e3f51 - correct
Events : 66836


Array Slot : 0 (0, failed)
Array State : U_ 1 failed

-bash-3.2$ sudo mdadm --examine /dev/sdb1
/dev/sdb1:
Magic : a92b4efc
Version : 1.0
Feature Map : 0x0
Array UUID : 08b6f7f1:b7f81bac:754a1ac8:b18cb525
Name : 0
Creation Time : Mon Feb 9 21:34:51 2015
Raid Level : raid1
Raid Devices : 2

Avail Dev Size : 5860532824 (2794.52 GiB 3000.59 GB)
Array Size : 5860532824 (2794.52 GiB 3000.59 GB)
Super Offset : 5860533080 sectors
State : active
Device UUID : 2cb22771:5d3923dd:7bea7098:8994d627

Update Time : Mon Jan 1 16:27:12 2024
Checksum : 16001cf7 - correct
Events : 7


Array Slot : 1 (0, 1)
Array State : uU

How can I add again to the RAID? And is there a way to see why it was removed from RAID?

 

[helpstar]

maybe the 2nd ssd has to be empty to join the array

 

[General_Cool]

maybe the 2nd ssd has to be empty to join the array

The RAID will automatically format the drive, does not have to be empty.

And is there a way to see why it was removed from RAID?

Are you sure the drive is not dead?