Lets keep it 'on list' for the benefit of others :) Henry, Andrew wrote: > Well, I want RAID1 for failover, and encryption for security and lvm to be able to add devices at a later stage. Yes, makes sense. Just a 'warning' (but that's too strong) to be aware that this layering may help uncover some bugs :) > Sorry, didn't mean that it will not boot at all. It boots but hangs on mounting the device I have given in fstab. OK >> (nb what distro/kernel are you using) > > Im using CentOS 5.1 x86_64 with 2.6.18-53 as OS and the LiveCD I used was Ubuntu 8.04 x86_64. OK. This kernel is very old wrt mainline although I suspect the distro will have backported many bugfixes and improvements I have no idea which :) >>> So after all that rambling, my question is: >>> >>> Why did /dev/md0 appear in fdisk -l when it had previously been sda/sdb >> even after successfully creating my array before reboot? >> fdisk -l looks at all the devices for partitions. >> sdc isn't there (hardware failure?) > > > Yes, it was hardware failure. The Sil controller had completely locked up on one port, probably due to all the dd'ing going on. I had to completely turn everything off and unplug cables. When I rebooted, I could then see my 2 500GB discs and my 320GB disc. Just to clarify: The 500GB discs are replacements for the single 320GB disc I have at the moment. The reason why I want to raid/dmcrypt/lvm is that I want extra security of RAID1 and I will lvm it because I plan to buy a second 320GB at a later stage and then RAID1 the two 320GBs in the same manner as above and add them to the same logical volume as the 2 500GB discs. OK. That's not good though. >>> How do I remove the array? Have I now done everything to remove it? >> mdadm --stop > > Do I not need to do -f /dev/sda -r /dev/sda to remove them properly?? starting and stopping an array is normal operation. Adding/removing disks is usually a recovery activity. To 'destroy' an array you should stop it and zero the superblocks on the component devices. > Ok, after power cycling it all, my 2 500GB discs came back according to fdisk -l. good. > Then I booted a LiveCD and dd'd sda and sdb from there, both the beginning of the device at 10MB and the last 256KB of the devices. OK - however random incantations of other commands are not recommended or needed for md on it's own. > I then rebooted into CentOS and they showed up as unpartitioned devices and /proc/mdstat was empty. OK. > I them proceeded to create a new array with mdadm --create and it says the same thing as before: that they are already part of an array! > I thought if I wiped the device and removed the config file it would wipe it but apparently there is something else I need to do? Well, fixing your email client to wrap lines helps! There is. Use --zero-superblock. Not aware of any bugs but you're on old systems here. > Anyway, I answered yes to the question of "do you want to continue" and it then says "out of sync, syncing discs" and *that* is when the /dev/md0 device appears when running fdisk -l, but now I can still see both sda and sdb. OK. all as expected. > Does /dev/md0 get registered with fdisk -l when there is an active array running? fdisk scans the system for block devices and when an array is running it shows up - usually by udev nowadays but mdadm will also created device nodes I think. > At least I can still see the discs now. So now it's been syncing all night and it's 50% complete. That's slow - my RAID5 takes 3hrs to do 320Gb - mirrors should be a *lot* faster. > I start to get the feeling that I need to use mdadm to stop, set fail and remove the devices to do this properly and to not dd them! Err, yes. > If I let the syncing continue, so that mdadm thinks the array is OK, can I then stop and remove them properly with mdadm? How? This is what distros are for... You are doing a lot of things that are not needed. > I want to wipe it all now and start again because I definitely want to autodetect on boot. Many people are confused by this - your distro will detect and mount the array on boot. It will then run lvm and dmcrypt over the top. You *do not* need (and should not use) kernel autodetect. You should assemble the array in the init scripts. David -- 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
