Concurrent access by two users - does it handle ok?

Hi, Jacob,

Even on your local filesystem, if two processes have the same file open and are writing concurrently, it's essentially a matter of luck as to which write happens first. Most operating systems provide an advisory locking facility that processes can use to detect and avoid concurrent access, but processes are not required to use these facilities. None of the SFTP or FTP server implementations I have seen use advisory locking in their default configurations.

So, to answer your question: ExpanDrive is at the mercy of whatever the SFTP or FTP server provides. If the server does not detect and prevent concurrent access, then ExpanDrive won't either. We play by the same rules that other processes are subject to. That means, if you are really editing and saving the file with two programs at once, you might get garbage. But that could also happen if you did the same thing without ExpanDrive, too.

Most applications that manipulate files mitigate this problem by reading the whole file, making changes in memory, then writing the whole file back. This is what programs like TextMate do, for example. Before writing changes, such programs check to see if the file was changed while you were editing it, and warns you if so.