Optimized Disk I/O in Solaris Unix

What we blithely call a "Disk I/O" is actually made up of several components, each of which may have an impact on overall performance. These layers may be broken down as follows for a typical I/O operation:

• POSIX: Application calls a POSIX library interface. (These frequently map directly to system calls, except for the asynchronous interfaces. These latter work via pread and pwrite.)
• System Call
• VOP
•    Filesystems 
•    Physical Disk I/O

Read more http://blogmee.info/index.php/optimized-disk-io-in-solaris-unix/

Disk Utilization

Disk Saturation

Usage Pattern

Disk Errors

Filesystem Performance

Filesystem Caching

Inode Cache

Buffer Cache

Inodes

Physical I/O

Direct I/O