As far as I know mdadm works the same way. (At least it was working
like this when this thread happened:
https://www.spinics.net/lists/raid/msg36962.html)
You can use a similar tactic that was recommended there: Don't
assemble a degraded RAID1 array without user interaction. You can do
this by changing the activation mode to complete in lvm.conf.
But then the server doesn't start at all which might also be costly.
The thread says that clock i not reliable eventually due to faulty hardware etc.
*BUT* why isn't there a way to 'stamp' the disks once clock is synced with the
internet ?
Let's compare two cases and two solutions.
solution 1:
write dates [date, known-devices] to the active disks
CASE: disk 1 appears sometimes. disk2 would have 'know-devices' disk2 only, so
disk1 could be identified as troublesome.
action mirror disk2 to1
CASE: split brain: disk1 appears, reboot disk2 appears, reboot both appear
Dates would be different. -> no mount
Not using the date info at all, thus could be using random numbers which would
be solution 2.
I don't have experience how often disks appear sometimes only.
To me it looks like having such strategy above which also could be implemented
in user space (but why ?)
would work in more cases very well cause the server would boot more often than
not.
Marc Weber
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