very match io waits

[boussetarachid]

hi all,
AIX 4.3.3 ML10 12 proc 8 Go Memeory ssa disks.

since i increase the MAXIMUM number of servers value for the Asynchronous I/O to 500, i have lot of waits in my system.

root@Uranus:/> sar 2 5
AIX Uranus 3 4 0051278A4C00 10/06/04
16:21:48 %usr %sys %wio %idle
16:21:50 18 7 47 28
16:21:52 11 8 58 23
16:21:54 13 13 58 16
16:21:56 6 4 57 34
16:21:58 9 2 52 36
Average 11 7 54 27

what is the optimal value for this parameter

 

[samjoo]

hi!
value for aio(maxserver) parameter is below

maxservers : number of disks accessed
asynchronously * 10
minservers : maxservers / 2

you must increase maxserver value after check number of aio process using "pstat -a|grep aio" command

 

[boussetarachid]

tnks samjoo,
i know this rule, but how can setup this value:
i ve 4 scsi internal disk, but the most of the activity is on the 14 ssa disks materialized by two logical disk on AIX.
shall i do 2 * 10 =20 (SSA)
or
(2+4)*10 (all disks).

tnks in advance

 

[samjoo]

hi!
you must calculate again if disk is made of raid.
i suggest that aio maxserver value is 2*10*8(cpu)=160 but you must set to value(160)that is in result of how many process of "pstat -a|grep aio" output