Hi Neil When testing 00raid1, found the md127 auto created when use "-B" to build a legacy array without superblocks, is it reasonable? 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 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html