Disk I/O and System Performance

The disk is used to store data and instructions used by your computer system. You can examine how efficiently the system is accessing data on the disk by looking at the disk access activity and terminal activity. See Chapter 64, Monitoring Performance (Tasks) for a discussion of the iostat and sar commands, which report statistics on disk activity. Managing and allocating disk space and dividing your disk into slices are discussed in Chapter 21, Disk Management (Overview).

If the CPU spends much of its time waiting for I/O completions, there is a problem with disk slowdown. Some ways to prevent disk slowdowns are:

• Keep disk space with 10% free so file systems are not full. If a disk becomes full, back up and restore the file systems to prevent disk fragmentation. Consider purchasing products that resolve disk fragmentation.

• Organize the file system to minimize disk activity. If you have two disks, distribute the file system for a more balanced load. Using Sun's Solstice DiskSuite(TM) product provides more efficient disk usage.

• Add more memory. Additional memory reduces swapping and paging traffic, and allows an expanded buffer pool (reducing the number of user-level reads and writes that need to go out to disk).

• Add a disk and balance the most active file systems across the disks.