Transactional NTFS (part 1/2)


Transactional NTFS and DotNet

Starting from Windows Vista and Windows Server 2008, Microsoft introduced a great new feature called Transactional NTFS (TxF).

It allows developers to write file I/O functions that are guaranteed to either succeed completely or fail completely.
Unfortunately there are no classes in the .NET framework that would allows us to perform, such operations.
We need to resort to P/Invoke to use the newly introduced functions CreateTransaction, CommitTransaction, RollbackTransaction and DeleteFileTransacted.

Note that I am using SafeFileHandle in method signatures instead of IntPtr to hold unmanaged resources which guarantees that they will be properly disposed even if the AppDomain was to stop.

The next thing is to define a helper class which would allow us to easily invoke those functions:

Sample with delete two files

Now suppose that you need to atomically delete two files: either both files are deleted or neither of them, but you never want to have only one of the two files deleted:

The method DeleteFile marks the file for deletion in the current transaction, but it will physically delete it only when the Commit method is called. Thanks to TxF and distributed transactions file and SQL operations can be performed inside the same transaction.

In part 2 we will see how to use the CreateFileTransacted function to perform atomic file read/writes.

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