Let me ask you the following re-factored version of your question and see if it illustrates the value of DRBD: > What is the advantage of "network I/O" over I/

Let me ask you the following re-factored version of your question and see if it illustrates the value of DRBD: > What is the advantage of "network I/O" over I/O? It seems to me that file copying is best left below the OS. Basically, DRBD gives you RAID-like replication of data across multiple physical hosts. This makes deployment of high-availability services stupidly easy, if sometimes less efficient than applicaiton-level replication protocols. For mail spools, NFS shares, or other simple file-based systems, though, it works pretty well.