On Tue, Jan 26 2016, yizhan wrote: > On 10/02/2015 03:55 PM, Neil Brown wrote: >> Yi Zhang <yizhan@xxxxxxxxxx> 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. > Hi Neil > I tried the mdadm --incremental, but it doesn't work, below is the > operation. > # mdadm -D /dev/md0 > /dev/md0: > Version : > Creation Time : Tue Jan 26 03:16:17 2016 > Raid Level : raid1 > Array Size : 2097152 (2.00 GiB 2.15 GB) > Used Dev Size : 2097152 (2.00 GiB 2.15 GB) > 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 > # mdadm -D /dev/md127 > /dev/md127: > Version : 1.2 > Raid Level : raid0 > Total Devices : 1 > Persistence : Superblock is persistent > > State : inactive > > Name : 0 > UUID : 13ada118:129135ff:686de7b7:4cb71d6d > Events : 17 > > Number Major Minor RaidDevice > > - 9 0 - /dev/md0 > # mdadm -I /dev/md127 > mdadm: /dev/md127 is not part of an md array. > # mdadm -I /dev/md0 > mdadm: cannot reopen /dev/md0: Device or resource busy. > > After I stopped md127, the md0 can be used again. If, after stopping md127, you try mdadm -I /dev/md0 again it will start /dev/md127 again. This is what udev does which causes md127 to appear in the first place. NeilBrown > > Thanks > Yi >> 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
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