Hi Team, A very good day to you all. I have a below scenario wherein mdraid array (raid0 originally) is failing to assemble after a node reboot, while array was expanding capacity (hence raid4). Can you please confirm that the forced recovery in this below scenario is correct and reliable always. 1/ create md array (raid0) example cmd: mdadm -C /dev/md/vol0 -n 2 --metadata 1.2 -c 1024 -l 0 /dev/sda /dev/sdb 2/ array goes full, so need to expand capacity Since this is a virtual environment, I am able to resize /dev/sda and /dev/sdb disks outside that are attached to my server node. After increasing the disk capacity backing disks /dev/sda and /dev/sdb, I am attempting to grow the array to the max capacity. 3/ Convert md array to raid 4 mdadm -G /dev/md/vol0 -l 4 4/ grow array to max capacity mdadm -G /de/vmd/vol0 --size max 5/ put it back to raid 0 mdadm -G /de/vmd/vol0 -l 0 In the above sequence, I only expand capacity by resizing the array elements and not by adding new disk to the array. While in the above sequence, I hit a power fail and node got rebooted. After node reboot, since array was in raid4 it failed to come online. ``` Jun 03 23:08:35 kernel: md/raid:md126: not clean -- starting background reconstruction Jun 03 23:08:35 kernel: md/raid:md126: device sda operational as raid disk 0 Jun 03 23:08:35 kernel: md/raid:md126: device sdb operational as raid disk 1 Jun 03 23:08:35 kernel: md/raid:md126: cannot start dirty degraded array. Jun 03 23:08:35 md/raid:md126: failed to run raid set. Jun 03 23:08:35 kernel: md: pers->run() failed ... ``` I recovered the array using the below sequence, given the array expansion was only through disk capacity resize. mdadm -S /dev/md126 /// which mapped to /dev/md/vol0 above mdadm -C /dev/md/vol0 -n 2 --metadata 1.2 -c 1024 -l 0 --assume-clean --force /dev/sda /dev/sdb This brought up the array back online and contents were okay too. So in the above sequence of actions, I want to understand the following: -- is the above method a reliable way to recover array incase there was a node reboot while in raid4 state? -- Please let me know your thoughts on recovery and data reliability on the array while recovering through the above sequence. Many thanks and kind regards for your help and insights. LN
