Yi Zhang [off-list ref] writes:
Hi Neil
When testing 00raid1, found the md127 auto created when use "-B" to build a legacy array without superblocks, is it reasonable?
This happens because udev notices a new device has appeared, looks
inside it, sees that it could be part of an md array, and so runs
"mdadm --incremental" on it.
Sometimes we want udev to do that. Sometimes we don't.
There is no easy way for udev to know what we want.
NeilBrown
pls check below detailed info:
+ mdadm -CR /dev/md0 --level=raid1 -n3 /dev/loop0 /dev/loop1 /dev/loop2
mdadm: /dev/loop0 appears to contain an ext2fs file system
size=58368K mtime=Thu Jan 1 08:00:00 1970
mdadm: Note: this array has metadata at the start and
may not be suitable as a boot device. If you plan to
store '/boot' on this device please ensure that
your boot-loader understands md/v1.x metadata, or use
--metadata=0.90
mdadm: /dev/loop1 appears to contain an ext2fs file system
size=38912K mtime=Thu Jan 1 08:00:00 1970
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.
+ mdadm --wait /dev/md0
+ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : active raid1 loop2[2] loop1[1] loop0[0]
19968 blocks super 1.2 [3/3] [UUU]
unused devices: <none>
+ mdadm -S /dev/md0
mdadm: stopped /dev/md0
+ mdadm -B /dev/md0 -l raid1 -n2 /dev/loop0 /dev/loop1
mdadm: array /dev/md0 built and started.
+ sleep 2
+ cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md127 : inactive md0[0](S)
19968 blocks super 1.2
md0 : active raid1 loop1[1] loop0[0]
20000 blocks super non-persistent [2/2] [UU]
unused devices: <none>
[root@dhcp-12-171 bug]# uname -r
4.2.0
[root@dhcp-12-171 bug]# mdadm -D /dev/md0
/dev/md0:
Version :
Creation Time : Mon Sep 7 20:21:20 2015
Raid Level : raid1
Array Size : 20000 (19.53 MiB 20.48 MB)
Used Dev Size : 20000 (19.53 MiB 20.48 MB)
Raid Devices : 2
Total Devices : 2
State : clean
Active Devices : 2
Working Devices : 2
Failed Devices : 0
Spare Devices : 0
Number Major Minor RaidDevice State
0 7 0 0 active sync /dev/loop0
1 7 1 1 active sync /dev/loop1
[root@dhcp-12-171 bug]# mdadm -D /dev/md127
/dev/md127:
Version : 1.2
Raid Level : raid0
Total Devices : 1
Persistence : Superblock is persistent
State : inactive
Name : dhcp-12-171.nay.redhat.com:0 (local to host dhcp-12-171.nay.redhat.com)
UUID : 40ace956:a9dd0793:f4984d2b:8431b92b
Events : 17
Number Major Minor RaidDevice
- 9 0 - /dev/md0
Best Regards,
Yi Zhang