There is some more information on iostat data at this location.

Column Disk I/O

Source /usr/bin/ iostat -x 30 2

Description
Two columns are used for determining the grade of the disk drives, the %busy column (%b) and the svc_t time column.

IDLE_DISK WHITE : %b < 5%

DISK_OK GREEN : %b >=5% && asvct_t < 30ms

BUSY_DISK AMBER : %b > 20% && (asvct_t > 30ms && asvct_t < 50ms)

BUSY_DISK RED : %b > 20% && asvct_t > 50ms

Caveats
In the raw data files, we only show lines where the %busy is 5 or higher. This method saves a lot of disk space on the reports. We always skip the first section of the iostat, these stats are since bootup. We look for the second section. The second tile "extended device statistics" indicates we are in the second section.

srtdate_iostat-xn: 20041027095232	SGT "iostat -xn 30 2 | nawk '{ if ($10 >4) print $0; if ( $1 == "extended") print $0;}'"
                    extended device statistics              
                    extended device statistics              
    r/s    w/s   kr/s   kw/s   wait actv wsvc_t asvc_t %w %b device
    7.2    0.5   85.7    7.0  0.0  0.1    0.8    8.5   1   5 d3
    6.2    8.3   66.7  162.0  0.0  0.3    0.2   19.8   0  10 c2t16d0
    6.2    8.3   68.0  162.0  0.0  0.3    0.3   20.2   0  10 c0t0d0
    6.5    0.7  114.7    3.0  0.0  0.1    0.4   14.9   0   5 faith-home1:/global/export/home1/55/yn128077
enddate_iostat-xn: 20041027095232	SGT

Column	Disk I/O
Source	/usr/bin/ iostat -x 30 2
Description	Two columns are used for determining the grade of the disk drives, the %busy column (%b) and the svc_t time column. IDLE_DISK WHITE : %b < 5% DISK_OK GREEN : %b >=5% && asvct_t < 30ms BUSY_DISK AMBER : %b > 20% && (asvct_t > 30ms && asvct_t < 50ms) BUSY_DISK RED : %b > 20% && asvct_t > 50ms
Caveats	In the raw data files, we only show lines where the %busy is 5 or higher. This method saves a lot of disk space on the reports. We always skip the first section of the iostat, these stats are since bootup. We look for the second section. The second tile "extended device statistics" indicates we are in the second section.