On 2004.03.01 02:09, Neil Brown wrote: > On Monday March 1, miquels@cistron.nl wrote: > > > > What do you think of that approach ? Converting from a 1 disk setup > > to a 2-disk RAID1 setup on an existing system is something that lots > > of people want to do, seeing that the software raid howto even has > > a few paragraphs dedicated to it. > > What I am thinking of doing is allowing: > > md=0,1,/dev/sda > > to assemble a raid1 array without a superblock which uses just > /dev/sda. > Then > > md=d0,1,/dev/sda root=/dev/md_d0p1 > > would boot off md/d0p1 instead of sda1, but it would be the same data. > > Then you would be able to add mirrors to this with something like: > > mdadm --grow /dev/md/d0 --disks=2 > mdadm /dev/md/d0 --add /dev/sdb > > and you could convert it into an array with a persistent superblock > using: > mdadm --grow /dev/md/d0 --persistent=yes > > The only difficult bit is the setting a persistent superblock means > reducing the size of the device, and I would like it to be hard to do > that in error, but not impossible to do it. Any progress on this? The right thing to do would probably be to check if the device actually has partitions - refuse to reduce the size of the device if it doesn't have any partitions, or if any partition overlaps with the MD superblock. That should be easy enough I think. But it would take changes in both userlevel tools (add --grow to mdadm) and the kernel, right ? So in the short run, I'll be better off by booting a Knoppix CD and running mdadm from there, I suppose. Are you interested in the patch I made to be able to initialize (but not run!) an array on a disk that is otherwise busy (i.e. can't be bd_claim()ed) ? Basically it just adds a SET_ARRAY_INFO_CONFONLY ioctl. I have patches for both the kernel and mkraid, and they're pretty simple. Mike. - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
