I'm attempting to implement multihost support of the MD for environments
such as carrier grade Linux. Multihost support allows the RAID array to
be claimed by a particular host via a unique ID (unique SCSI host ID,
FibreChannel WWN, or geographical address of a chassis blade. That way
another host that can access the disks do not claim the same disks that
are used by the RAID array.
Why not just use SCSI reservations?
I would like to store a 64bit unique ID on the superblock of the device. The least intrusive way IMHO to do this is implementing the feature via the management app such as mdadm in userland. However, it seems that after I instruct the kernel to create the MD array via mdadm, the kernel starts out with a blank superblock and clobbers the
If you write a valid superblock to the disk and then assemble the array, the superblock doesn't get clobbered.
data I have stored on the superblock via mdadm. Would it be acceptable to modify the kernel such that the unique ID info is preserved during the creation of the superblock by the kernel? Example patch follows:
As for adding additional fields to the various superblock formats, you'd have to ask Neil if he's open to that.
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