Not sure which is the defective component: raidtools, e2fsprogs, perhaps even the kernel. Configured partitions on 3 SCSI disks into a RAID-5 array, using the RedHat installation tool. Filesystem mounted, array allowed to sync. Powered down system. If I disconnect /dev/sdb or /dev/sdc and then power up: system correctly detects missing disk and runs in degraded mode. If I disconnect /dev/sda and then power up: e2fsck fails with the following error: "The superblock could not be read or does not describe a correct ext2 filesystem. If the device is valid and it really contains an ext2 filesystem (and not swap or ufs or something else), then the superblock is corrupt, and you might try running e2fsck with an alternate superblock: e2fsck -b 8193 <device> fsck.ext2: Bad magic number in super-block while trying to open /dev/md2" I have tried running "e2fsck -b 32768" (the correct location of the first superblock) and also the second & third superblocks. Same error. My /etc/raidtab specifies persistent-superblock. =================================================================== /proc/mdstat before disconnecting drive 0 (sda): Personalities : [raid1] [raid5] read_ahead 1024 sectors md0 : active raid1 sdc1[2] sdb1[1] sda1[0] 2048192 blocks [3/3] [UUU] md2 : active raid5 sdc5[2] sdb5[1] sda5[0] 4096384 blocks level 5, 64k chunk, algorithm 0 [3/3] [UUU] md1 : active raid1 sdc7[2] sdb7[1] sda7[0] 24000 blocks [3/3] [UUU] =================================================================== /proc/mdstat AFTER disconnecting drive 0 and booting (note that sdc became sdb, sdb became sda): Personalities : [raid1] [raid5] read_ahead 1024 sectors md0 : active raid1 sdb1[2] sda1[1] 2048192 blocks [3/2] [_UU] md2 : active raid5 sdb5[2] sda5[1] 4096384 blocks level 5, 64k chunk, algorithm 0 [3/2] [_UU] md1 : active raid1 sdb7[2] sda7[1] 24000 blocks [3/2] [_UU] unused devices: <none =================================================================== /etc/raidtab (md2 -- the RAID-5 array -- is at the bottom): raiddev /dev/md0 raid-level 1 nr-raid-disks 3 chunk-size 64k persistent-superblock 1 #nr-spare-disks 0 device /dev/sda1 raid-disk 0 device /dev/sdb1 raid-disk 1 device /dev/sdc1 raid-disk 2 raiddev /dev/md1 raid-level 1 nr-raid-disks 3 chunk-size 64k persistent-superblock 1 #nr-spare-disks 0 device /dev/sda7 raid-disk 0 device /dev/sdb7 raid-disk 1 device /dev/sdc7 raid-disk 2 raiddev /dev/md2 raid-level 5 nr-raid-disks 3 chunk-size 64k persistent-superblock 1 #nr-spare-disks 0 device /dev/sda5 raid-disk 0 device /dev/sdb5 raid-disk 1 device /dev/sdc5 raid-disk 2 =================================================================== fdisk /dev/sda (sdb and sdc are identical): Disk /dev/sda: 255 heads, 63 sectors, 1106 cylinders Units = cylinders of 16065 * 512 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 255 2048256 fd Linux raid autodetect /dev/sda2 256 1106 6835657+ 5 Extended /dev/sda5 256 510 2048256 fd Linux raid autodetect /dev/sda6 511 527 136521 82 Linux swap /dev/sda7 528 530 24066 fd Linux raid autodetect