There are two methods of transferring data between memory and disk:
The two forms of AIO supported are the aio(HW) driver and the POSIX.1b aio functions.
See ``Viewing AIO activity'' for information about how to monitor AIO activity.
Synchronous I/O operations to the raw disk device force the process requesting the operation to wait for it to complete. Database applications typically use synchronous I/O to ensure the integrity of the data being written to disk. For example, the journal logs that a database uses to recover in the event of system failure are written to disk using synchronous I/O.
In a similar way, the system maintains a namei cache (for translating names to inodes) of most recently used filenames in order to speed up locating files within filesystems. See ``How the namei cache works'' for a description of its operation.
Finally, the multiphysical buffers use a small pool of memory (generally 160KB to 256KB in size). They are used for various purposes as described in ``How multiphysical buffers are used''.
For a description of how to monitor the activity of block devices including disks, see ``Viewing disk and other block I/O activity''.
Disk I/O and networked filesystem
(such as NFS®)
performance are affected by filesystem
and other filesystem-related factors as described in
``Filesystem factors affecting disk performance''.