Linux System Administration
Filesystems (Continued)
RAID Configuration - Starting an Array
$ mdadm -E /dev/sdc1
/dev/sdc1:
Magic : a92b4efc
Version : 00.90.00
UUID : 84788b68:1bb79088:9a73ebcc:2ab430da
Creation Time : Mon Sep 23 16:02:33 2002
Raid Level : raid0
Device Size : 17920384 (17.09 GiB 18.40 GB)
Raid Devices : 4
Total Devices : 4
Preferred Minor : 0
Update Time : Mon Sep 23 16:14:52 2002
State : clean, no-errors
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Checksum : 8ab5e437 - correct
Events : 0.10
Chunk Size : 128K
Number Major Minor RaidDevice State
1 8 33 1 active sync /dev/sdc1
0 0 8 17 0 active sync /dev/sdb1
1 1 8 33 1 active sync /dev/sdc1
2 2 8 49 2 active sync /dev/sdd1
3 3 8 65 3 active sync /dev/sde1
In this case we can tell that
/dev/sdc1
belongs to a RAID-0 made up of a total of four member disks.
A UUID is a 128-bit number that is guaranteed to be reasonably unique on both the local system and across other systems.
It is a randomly generated using system hardware and timestamps as part of its seed.
When an array is created, the md driver generates a UUID for the array and stores it in the md superblock.
You can use the UUID as criteria for array assembly.
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