This article is long, please read with kind patience.
Two questions about creating soft RAID by mdadm:
1. Need I to restart system after fdisk, and when start up again, do I have to format the partitions before create RAID?
I'm now reading some books about RHCE exam written by Michal Jang. He said, "When you configure RAID, you will format same spaces twice, the first format the patitions that make up the array, while the second format the RAID as if they were new partitions".
From my practices in lab, it seems that I must reboot the OS to activate new partitions. Later, I issue mdadm to create array while skip the first formation step above, the array is also built successfully.
I've googled for many pages, and do not confirm whether I did right things yet.
2. What's the meaning of "/dev/md0: No md super block found, not an md component."?
Here's my process:
fdisk (new partitions assigned fd)--> reboot OS --> mdadm --create /dev/md0 --level=1 --raid-devices=2 /dev/sda5 /dev/sda6 --spare-devices=1 /dev/sda7
The array is created successfully without error, then check the status:
[root@Muyang ~]# mdadm --query /dev/md0
/dev/md0: 101.88MiB raid1 2 devices, 1 spare. Use mdadm --detail for more detail.
/dev/md0: No md super block found, not an md component.
[root@Muyang ~]# mdadm --detail /dev/md0
Version : 00.90.01
Creation Time : Wed Jan 10 10:03:33 2007
Raid Level : raid1
Array Size : 104320 (101.88 MiB 106.82 MB)
Device Size : 104320 (101.88 MiB 106.82 MB)
Raid Devices : 2
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent
Update Time : Wed Jan 10 10:03:37 2007
State : clean
Active Devices : 2
Working Devices : 3
Failed Devices : 0
Spare Devices : 1
Number Major Minor RaidDevice State
0 8 5 0 active sync /dev/sda5
1 8 6 1 active sync /dev/sda6
2 8 7 -1 spare /dev/sda7
UUID : 345a71c9:76dc0d4c:8e753193:96fde17c
Events : 0.2
Superblock records the array information, and I think /dev/md0 means meta device of array, why does it say "not found md super block"? Is the concept of "superblock" based on hardware, not devices as "/dev/md0"?
Please give me some hints.
Thanks in advance.