Robbie:

This would require real-time replication of all shared folders since you cannot predict which DC a user will log into. Additionally, if you log into multiple computers at the same time, you might end up with shares to different folders, which then cannot be replicated.

The recommended solution for a fault-tolerant setup would be either a cluster-aware external RAID storage device with the RAID controller connected to two servers at the same time, or some kind of NAS/SAN setup.
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