On Fri, 29 Oct 2010 15:18:09 +0100 Mathias BurÃn <mathias.buren@xxxxxxxxx> wrote: > Question 3: Before I created this RAID5 array I did a quick RAID0 test > array just for fun, using 2 full devices (not partitions). Now I have > this: > > mdadm --examine --verbose --scan > ARRAY /dev/md/raid0-test level=raid0 metadata=1.2 num-devices=2 > UUID=b84cc081:1ae27b49:d5ae466c:377ba300 name=ion:raid0-test > devices=/dev/sdf,/dev/sdb > ARRAY /dev/md/0 level=raid5 metadata=1.2 num-devices=6 > UUID=e6595c64:b3ae90b3:f01133ac:3f402d20 name=ion:0 > devices=/dev/sdg1,/dev/sdf1,/dev/sde1,/dev/sdd1,/dev/sdc1,/dev/sdb1 > > Is it safe to erase the raid0-test superblocks on device /dev/sdb and > /dev/sdc or will it interfere with my RAID5 array (which is lying on > top of partitions) ? It should be safe to mdadm --zero-superblock /dev/sdf /dev/sdb As you have 1.2 metadata, that info will be 4K from the start of the device. Depending on how you partitioned the devices, that is either in dead space between the partition table and the first partition, or it is in dead space in the first partition just before the md metadata. So the old metadata is still visible, creating the new arrays clearly didn't over-write it, so they don't really care what is there... That statement isn't 100% general. A block in the data area of the new array could be unchanged by creating an array, yet changing it could still corrupt parity. However you can be certain that the metadata for a whole-device array does not lie in the data area for a partitioned array of the same metadata type. 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
