Good scalable fault-tolerant in-memory database with LINQ support for .NET

Are there are good in-memory transactional databases that support LINQ and SQL Server persistance? I'd like to create a full representation of a large data store in memory and have it commit to a SQL Server Database in a lazy fashion, but still k开发者_StackOverflow中文版eep some level of fault tolerance by scaling it out horizontally. I don't want to rely on non-relational datagrams like CouchDB.

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SQLite supports in-memory databases has transaction support and has a Linq provider as well.

As for the SQL Server persistance, I think you would be on your own to code up something for doing lazy transfers to a backing SQL Server database.

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SQL Server with an ORM tool and possibly a caching solution.