Need to ensure OLTP Database that uses a SAN remains available if any of the servers fail, need to minimize the amount of storage used

Here is a question about MS SQL Server administration.

I Need to ensure OLTP Database that uses a SAN (Storage Area Network) remains available if any of the servers fail, I need to minimize the amount of storage used by the database. Which configuration should you use?

The correct answer is

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Two servers configured in a Windows Failover Cluster in the same data center. SQL Server configured as a clustered instance.

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I can't figure out why using Windows Failover Cluster would result minimized storage usage.