- JFS - Journaled File System
- CIO - Concurrent I/O (uses JFS)
- DIO - The Direct I/O option
AIX has the Concurrent IO (CIO) method within their JFS filesystem, allowing the use of JFS while achieving fast I/O (almost as fast as raw devices). Raw partitions in AIX are quite cumbersome and CIO is a great alternative since you get the ease of administration and the speed of “almost raw”.
However, high-DML database may want to use direct I/O (DIO instead of JFS or CIO. See these notes on using Oracle AIX with direct I/O which is implemented with the AIX "dio" option and the init.ora parameter
filesystemio_options:Oracle init.ora: filesystemio_options = SETALL or JFS2 mount option: mount –o dio /oradata/ts1.dbf
IBM says that direct I/O (DIO) tends to benefit heavily random access workloads while CIO tends to benefit heavily update workloads.
If planning to use JFS2 CIO, be sure to isolate online redo logs and control files in a separate file system that was created with agblksize=512.
File systems which contain Oracle data (.dbf) files should be created with agblksize=4096 if db_block_size >= 4K or agblksize=2048 if db_block_size=2K.
On CIO-mounted filesystems that contain datafiles, the database block size needs to be multiple of agblksize.
Not all workloads benefit from the use of CIO (i.e. they get more benefit from filesystem caching). In some cases, it may be desirable to create multiple filesystems and allocate files based on their anticipated workload characteristics
Therefore, individual filesystems could be mounted in CIO mode, or default caching mode, depending on the I/O characteristics of the files within the particular filesystem