Description of problem:
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If migration process reads data that is not yet healed because source brick is down it may lead to data loss


Snippet:
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This is same old, AP vs CP systems. 2-way replication is AP system. User
knows this. If he does copy at the time because the brick was down he
will lose the data in the new copy. Not the source itself. But with
rebalance/tiering this problem becomes severe as the source file is lost.

One way to fix it is to give an option in afr where reads won't succeed
if all the bricks are not up. Rebalance and tiering should use it. We
don't have this problem in 3-way replica and arbiter.


Version-Release number of selected component (if applicable):
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3.7.5-19

How reproducible:
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