Ross S. W. Walker wrote:
>
>>>>> If you have a disk with several partitions set up as members of a
>>>>> raid1 md devices, can you make a dd image of that disk to replace its
>>>>> matching drive with identical partitions or are there differences
>>>>> between the mirrored partitions?
>>>> you can 'dd' the MBR and then re-add the partitions to the raid for
>>>> resyncing with 'mdadm'.
>>>>
>>>> # dd if=/dev/sda of=/dev/sdb bs=512 count=1
>>>> # mdadm /dev/md0 --add /dev/sdb1
>>>> # mdadm /dev/md1 --add /dev/sdb2
>>>>
>>>> If you want to really make sure you got everything you could dd the
>>>> whole first track with:
>>>>
>>>> # dd if=/dev/sda of=/dev/sdb bs=512 count=63
>>>>
>>>> -Ross
>>>>
>>> Or sfdisk -d /dev/sdX | sfdisk /dev/sdY
>>> where x is source and y is the target.
>>> This will work across drives that have slight geometry differences.
>> What I was hoping to do was to take the grub setup, the partitioning
>> info and the contents in one shot and have the disks pair automatically
>> when booted. They didn't - but I think the other parts worked.
>>
>> Now, is there a way to change the uuid on a running raid1 set? I'd
>> prefer that if the split and re-paired disks ever find their way back to
>> the same machine that they not sync again.
>
> 'mdadm' writes a listing of the devices in the array to the md
> superblock and orders them by number,major,minor. You cannot add
> another device to the array with the same tuple.
Isn't this updated at detect time so the device minor's should always be
different?
> If you dd the first sector of the drive though you will duplicate
> the partition table and grub boot loader to the other drive. Then
> md-device-mapper will take care of copying the data over.
I'm curious as to why 2 complete dd'd copies don't pair at boot. One
comes up running and it does work to mdadm --add the partner partitions
and after the resync they do automatically pair at boot.
--
Les Mikesell
lesmikesell at gmail.com