Direct I/O for NFS

DIO allows applications to perform reads and writes directly to the NFS server without going through the NFS client caching layer (Virtual Memory Manager), or incurring the associated overhead of caching data.

Under DIO, application I/O requests are serviced using direct Remote Procedure Calls (RPC) to the NFS server. You can set DIO using the AIX® dio mount option. Without the mount option, you can also enable DIO per-file by using the AIX O_DIRECT open() flag.

Servicing NFS direct I/Os might require multiple RPCs to the server, depending on the I/O request size and the maximum wire transfer size permitted by the server and client. For more information about DIO, see the -o option for the mount command.