On Mon, 09 Dec 2013 10:56:32 +1100 Adam Goryachev <mailinglists@xxxxxxxxxxxxxxxxxxxxxx> wrote: > On 09/12/13 10:17, NeilBrown wrote: > > On Sun, 8 Dec 2013 17:03:22 -0600 Hai Wu <haiwu.us@xxxxxxxxx> wrote: > > > >> This is something I am not aware of, thanks! > >> > >> In this case, do I have to worry about cases where the new drive might not be able to boot (this is raid1 with 2 drives, and both drives need to be able to boot up the server by themselves in case the other drive fails later)? I remember I had to do the following before for the new drive: > >> > >> grub> root (hd0,0) > >> > >> Is that still the case here if marking it as 'spare'? > > If you want the new drive to boot and the boot sector is not covered by any > > md array, then you have to update the boot sector yourself. > > > > You can presumably get udev to run some command which will write a boot > > sector out. However I'm not an expert on boot sector management so cannot > > really advise you. > Hi Neil, > > I like the way you phrased that :) > > I just wanted to clarify one point, it there a specific MD metadata > version (I'm assuming either 1.0 or 1.2) which could be applied to an > entire device MD array which would allow the automatic sync of the boot > sectors/etc > > ie, something like: > mdadm --create /dev/md3 --level=raid1 --metadata=1.2 /dev/sda /dev/sdb > > then writing the boot sector information to /dev/md3 > mdadm --manage /dev/md3 --fail /dev/sdb > mdadm --manage /dev/md3 --remove /dev/sdb > mdadm --manage /dev/md3 --add /dev/sdc > > Then, shutdown, remove sda and sdb > > Would you expect the system to boot successfully from sdc (assuming the > BIOS will boot from it, and that the OS will "find" the correct boot and > root device.... > > In the past I've always used partitions for MD, but this might be a good > reason to use whole devices if it would solve the issue of the boot > sector information. > > Regards, > Adam If you use --metadata=1.0 then everything from the very start of the device to near the end is mirrored. If having identical boot blocks on every device works (which I think it does, but I'm no expert), then using --level=raid1 --metadata=1.0 on whole devices (not partitions) would remove the need to worry further about boot sectors. NeilBrown
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