Hi Why would the superblock magic be zero on a newly created RAID-1 set? I get this error when the kernel (2.6.17.7) boots: md: Autodetecting RAID arrays. md: invalid raid superblock magic on sda1, found 0x0 not 0xa92b4efc md: sda1 has invalid sb, not importing! md: invalid raid superblock magic on sda2, found 0x0 not 0xa92b4efc md: sda2 has invalid sb, not importing! md: invalid raid superblock magic on sdb1, found 0x0 not 0xa92b4efc md: sdb1 has invalid sb, not importing! md: invalid raid superblock magic on sdb2, found 0x0 not 0xa92b4efc md: sdb2 has invalid sb, not importing! md: autorun ... md: ... autorun DONE. (I modified md.c so that it prints out "found xxxx not 0xa92b4efc") I have a monolithic kernel, compiled for RAID-1. Once the system is up and running, mdadm brings up the RAID arrays fine: # cat /proc/mdstat Personalities : [raid1] md1 : active raid1 sda2[0] sdb2[1] 506036 blocks super 1.0 [2/2] [UU] md0 : active raid1 sda1[0] 312062456 blocks super 1.0 [2/1] [U_] unused devices: <none> It is deliberately degraded, so that I can boot until I fix this problem. # dpkg -l mdadm | grep mdadm ii mdadm 2.5.3.git200608202239-7 tool to administer Linux MD arrays (software RAID) I've re-created the RAID set a couple of times just to make sure that I did it correctly. Here's how: mdadm -C /dev/md0 --level=raid1 --raid-devices=2 /dev/sda1 missing As I understand it, this can't be an issue with my config files, because the error occurs *before* the filesystem is mounted. # fdisk -l /dev/sd[a-z] Disk /dev/sda: 320.0 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 38850 312062593+ fd Linux raid autodetect /dev/sda2 38851 38913 506047+ fd Linux raid autodetect Disk /dev/sdb: 320.0 GB, 320072933376 bytes 255 heads, 63 sectors/track, 38913 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 38850 312062593+ fd Linux raid autodetect /dev/sdb2 38851 38913 506047+ fd Linux raid autodetect Some info about the (brand new) disks: # hdparm -I /dev/sda ATA device, with non-removable media Model Number: WDC WD3200YS-01PGB0 Serial Number: WD-WCAPD2664999 Firmware Revision: 21.00M21 Standards: Supported: 7 6 5 4 Likely used: 7 Configuration: Logical max current cylinders 16383 16383 heads 16 16 sectors/track 63 63 -- CHS current addressable sectors: 16514064 LBA user addressable sectors: 268435455 LBA48 user addressable sectors: 625142448 device size with M = 1024*1024: 305245 MBytes device size with M = 1000*1000: 320072 MBytes (320 GB) Many thanks, Thomas - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html