Iostat output

ITEM: RTA000079099

I tried the command on the RS/6000 connedted with 7135-110.                     
$ iostat                                                                        
TTY:     TIN     TOUT     CPU:  % USER    % SYS    % IDLE    % IOWAIT           
         0.7     22.6            17.8     51.8      30.3       0.2              
DISKS:     % TM_ACT   KBPS    TPS     KB_READ   KB_WRTN                         
HDISK0        0.3     1.4     0.3     117405    232938                          
HDISK1        0.1     0.2     0.0       2816     48588                          
CD0           0.0     0.0     0.0       7882         0                          
DAC0          0.0     0.0     0.0          0         0                          
HDISK2        0.1     1.2     0.2     118641    173640                          
HDISK2 is connected with DAC0 ( Disk Array Controller ).                        
HDISK0 and HDISK1 are connected with SCSI adapter.                             
I heard that iostat report i/o statics for tty, disk, and cdrom.                
But this output includes the Disk Array Controller, and it's value              
are all zero.                                                                   
So, my questions as follows.                                                    
(1) Is the Disk Array Controller considered as Disk?                            
(2) If (1) is true, Does iostat have any function for accounting DAC0,          
   doesn't it?                                                                  
    The performance commands in AIX were not designed to work with              
    RAID devices.  Since these are composed of multiple disks the               
    information returned for a LUN is not reliable.  The DAC is                
    not considered a hdisk, and iostat does not have a way of                   
    getting performance numbers from the DAC.  Also, as before the              
    numbers returned for a LUN are not necessarily accurate.                    
S e a r c h - k e y w o r d s:                                                  
IOSTAT AND 7135                                                                 

WWQA: ITEM: RTA000079099 ITEM: RTA000079099
Dated: 02/1995 Category: ITSAI6000CO
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