When was shadowing first introduced in IB? Was RAID popular at the time?
What is the original reasoning for shadowing and what is the future of
shadowing?

It seems only IB/FB (of some other DB's I know) has feature like this.
Other DB's seem to go the way of WAL (write ahead log) + snapshot
backup, but I think shadowing is much simpler for recovery and backup.
What is the Firebird architects' view on this?

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dave