On Friday October 26, gcormier@xxxxxxxxx wrote: > Can someone help me understand superblocks and MD a little bit? > > I've got a raid5 array with 3 disks - sdb1, sdc1, sdd1. > > --examine on these 3 drives shows correct information. > > > However, if I also examine the raw disk devices, sdb and sdd, they > also appear to have superblocks with some semi valid looking > information. sdc has no superblock. If a partition starts a multiple of 64K from the start of the device, and ends with about 64K of the end of the device, then a superblock on the partition will also look like a superblock on the whole device. This is one of the shortcomings of v0.90 superblocks. v1.0 doesn't have this problem. > > How can I clear these? If I unmount my raid, stop md0, it won't clear it. mdadm --zero-superblock device name is the best way to remove an unwanted superblock. Ofcourse in the above described case, removing the unwanted superblock will remove the wanted one aswell. > > [root@zeus ~]# mdadm --zero-superblock /dev/hdd > mdadm: Couldn't open /dev/hdd for write - not zeroing As I think someone else pointed out "/dev/hdd" is not "/dev/sdd". NeilBrown - 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
