Layman answer to the %wio from sar output

[Belinda Dermody]

I have the following output from sars and I am curious what the %wio column indicates, I know what the man pages states but a little more insite in laymans terms would be nice. Especially when the %wio goes from very low to a lot higher numbers.


22:10:59 0 1 0 5 94
1 1 0 6 92
system 1 0 6 93
22:20:58 0 0 0 1 99
1 0 0 0 100
system 0 0 0 99
22:30:57 0 0 0 34 66
1 1 1 30 68
system 1 0 32 67
22:40:56 0 1 1 38 61
1 1 1 60 38
system 1 1 49 50
22:50:55 0 1 0 30 69
1 1 1 66 32
system 1 1 48 51
Tuesday:
06:01:00 0 1 1 59 38
1 1 1 66 31
system 1 1 63 35
06:10:59 0 11 6 54 29
1 3 2 79 15
system 7 4 66 22
06:20:58 0 1 1 68 31
1 1 1 75 23
system 1 1 71 27
06:30:57 0 1 1 66 33
1 1 1 76 22
system 1 1 71 27
06:40:56 0 1 1 70 28
1 1 1 72 25
system 1 1 71 27
06:50:55 0 0 1 66 33
1 0 1 76 23
system 0 1 71 28
07:01:00 0 1 1 40 58
1 1 1 67 31
system 1 1 53 45
07:10:59 0 1 1 36 63
1 1 1 64 34
system 1 1 50 49
07:20:58 0 7 2 45 46
1 6 2 52 40
system 6 2 48 43
07:30:57 0 1 1 28 71
1 1 1 42 56
system 1 1 35 63
07:40:56 0 0 0 0 99
1 0 0 0 99
system 0 0 0 99
07:50:55 0 0 0 1 99

[Matti_Kurkela · Accepted solution]

Basically, high %wio means that the processor(s) would have something to do, but it can't do it before some I/O operation (often disk read/write) is complete.

If the performance is "good enough", high %wio means that the current process is not doing heavy "number crunching", but is mainly just "pushing data around". The processor could do more if the I/O would just happen faster. A good thing to keep in mind when planning future upgrades...

If you need more performance, first check that there is no RAM shortage. RAM shortage often leads to lots of data moved repeatedly in/out of swap, so the CPU does not get much useful work done in between.

If RAM shortage is not the problem, look at the I/O device activity (e.g. sar -d). If some disk is hit harder than the others, striping the content of that disk to two or more disks (preferably on separate buses) would be a good idea.

[Steve Steel]

Hi

This forum reference is interesting

http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=138987


Gte glance if you have performance problems


Steve Steel

[Belinda Dermody]

Steve I can't get to the thread

[Belinda Dermody]

Steve but your reponse led me to other threads so if you just do respond I will assign more points to you...