NFS DIO and CIO support

AIX 5L Version 5.3 with the 5300-03 Recommended Maintenance package supports direct I/O and concurrent I/O in the NFS client for the version 3 and 4 protocols. DIO and CIO only involve the client.

Using DIO and CIO, data center workloads such as databases and high performance computing applications can experience higher levels of performance, coupled with reduced system CPU and memory resources, while maintaining the benefits of centralizing file-based storage and its associated management of back-end systems.

I/O is often nonsequential, and often applications do not benefit from data caching at the NFS client, or the applications do all the advanced caching. These applications benefit when NFS does not cache, perform read prediction, or use write-behind mechanisms. In addition, some applications such as databases are not dependent on POSIX single-site semantics, which serialize reads against writes. These applications issue concurrent reads and writes, but these applications are responsible for the consistency and coordination of such operations.