I've had to (temporary) reduce my RAID5-Array, so that there are four out of five disks available. Things getting worse as my system crashed during write process. After reboot the system wants to start "Background Reconstruction" as it normally does to an intact array to reconstruct the missing redundancy. As the array is degraded, this reconstruction does not start (see https://raid.wiki.kernel.org/index.php/Tweaking,_tuning_and_troubleshooting#Autodetection last paragraph on what the Reconstruction does).
I want to make my array active again but a mdadm --run /dev/md127 produces an input/output error (same "background reconstruction"-message under syslog). I know that I am loosing some MB of data- but how can I get my array back to work?
/dev/md127: Version : 1.2 Raid Level : raid5 Used Dev Size : 1360148480 (1297.14 GiB 1392.79 GB) Raid Devices : 5 Total Devices : 4 Persistence : Superblock is persistent Update Time : Fri Jun 14 10:54:22 2013 State : active, degraded, Not Started Active Devices : 4 Working Devices : 4 Failed Devices : 0 Spare Devices : 0 Layout : left-symmetric Chunk Size : 512K Name : mars:RA UUID : 05c6d9f1:87571dc6:ee0d9f6b:c0b0c320 Events : 159201 Number Major Minor RaidDevice State 7 8 18 0 active sync /dev/sdb2 8 8 66 1 active sync /dev/sde2 2 0 0 2 removed 5 8 34 3 active sync /dev/sdc2 9 8 50 4 active sync /dev/sdd2