Input Output statistics ( iostat )

iostat reports
>terminal and disk I/O activity and
>CPU utilization.

iostat’s activity class options default to tdc (terminal, disk, and CPU).

The values to look from the iostat output are:* Reads/writes per second (r/s , w/s)
* Percentage busy (%b)
* Service time (svc_t)
 If a disk shows consistently high reads/writes along with ,
the percentage busy (%b) of the disks is greater than 5 percent, and
the average service time (svc_t) is greater than 30 milliseconds,
then one of the following action needs to be taken

1.) Tune the application to use disk i/o more efficiently by modifying the disk queries and using available cache facilities of application servers .

2.) Spread the file system  of the disk on to two or more disk using disk striping feature of volume manager /disksuite etc.

3.) Increase the system parameter  values for inode cache , ufs_ninode , which is Number of inodes to be held in memory. Inodes are cached globally (for UFS), not on a per-file system basis

4.) Move the file system to another faster disk /controller or replace existing disk/controller to a faster one.