Hello all, i have already had a discussion on the software raid mailinglist and i want to switch to this one :) I am having a really strange problem with my md0 device running centos7. after a new start of my server the md0 was gone. now after trying to find the problem i detected the following: Booting any installed kernel gives me NO md0 device. (ls /dev/md* doesnt give anything). a 'cat /proc/partitions show me now /dev/sd[a-d]1 partition. partprobe and a mdadm assemble gives me "disk busy" [root at quad live]# cat mdstat Personalities : [raid6] [raid5] [raid4] [raid10] unused devices: <none> [root at quad ~]# partprobe device-mapper: remove ioctl on WDC_WD20EFRX-68AX9N0_WD-WMC301255087p1 failed: Device or resource busy Warning: parted was unable to re-read the partition table on /dev/mapper/WDC_WD20EFRX-68AX9N0_WD-WMC301255087 (Device or resource busy). This means Linux won't know anything about the modifications you made. .... .... [root at quad ~]# mdadm --assemble --force /dev/md0 /dev/sda1 /dev/sdb1 /dev/sdc1 /dev/sdd1 mdadm: /dev/sda1 is busy - skipping mdadm: /dev/sdb1 is busy - skipping mdadm: /dev/sdc1 is busy - skipping mdadm: /dev/sdd1 is busy - skipping booting from a usb stick for rescue my centos everything works. the md0 device exists and is mounted. (rw). [root at quad usb-rescue]# cat mount | grep '/data' /dev/mapper/data-store on /mnt/sysimage/store type xfs (rw,noatime,seclabel,attr2,largeio,nobarrier,inode64,logbufs=8,logbsize=256k,sunit=256,swidth=768,noquota) /dev/mapper/data-tm on /mnt/sysimage/var/lib/vdr/video type xfs (rw,noatime,seclabel,attr2,largeio,nobarrier,inode64,logbufs=8,logbsize=256k,sunit=256,swidth=768,noquota) 3rd option: i am booting the installed rescue kernel from disk: i am getting a md0 device, but its not started. when i stop the md0 i cant assemble it anymore (disk busy) /dev/md0: Version : 1.2 Creation Time : Wed Aug 20 19:28:52 2014 Raid Level : raid5 Used Dev Size : 1953382272 (1862.89 GiB 2000.26 GB) Raid Devices : 4 Total Devices : 4 Persistence : Superblock is persistent Update Time : Thu Aug 17 22:38:14 2017 State : active, Not Started Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 128K Name : quad.core.sartori.at:0 (local to host quad.core.sartori.at) UUID : 9d020f27:c0542472:b95a18d2:5741114d Events : 25458 Number Major Minor RaidDevice State 0 8 1 0 active sync /dev/sda1 1 8 17 1 active sync /dev/sdb1 2 8 33 2 active sync /dev/sdc1 4 8 49 3 active sync /dev/sdd1 anyone got an idea, in which direction the problem could be? more logs needed? please help, i have no ideas anymore. regards Andy