UNIX for Dummies Questions & Answers

Hi,

# SAR -u 5 5 shows this

10:01:32 AM CPU %user %nice %system %iowait %idle
10:01:37 AM all 1.90 0.00 1.20 96.90 0.00
10:01:42 AM all 1.30 0.00 1.70 97.00 0.00
10:01:47 AM all 4.30 0.00 1.60 94.11 0.00
10:01:52 AM all 1.50 0.00 1.20 97.30 0.00
10:01:57 AM all 1.90 0.00 1.10 97.00 0.00
Average: all 2.18 0.00 1.36 96.46 0.00

I think this %iowait is too much. I noticed when it's about 0.5% server is very okay, but when more than 90% it's very very slow.

What is %iowait. Can anyone explain more about this and how can I fix it ?

Thanks

I/O wait is the time your system is waiting for input/output. This can apply to disk, tape, or network connections. So when you notice your system's i/owait is high it's waiting for I/O transactions to finish - if you get enough processes requesting i/o ( most do ), you system will slow down. You can check with netcat, top, iostat, etc. to try and find you "bottle neck".

But depending on the system's main function you maybe able to make an educated guess on where your problem is.

Tom de