High %wa , but iotop shows low disk usage

postcd · 05-02-2014, 08:26 AM

Hello,

im running rsync with --bwlimit 10000 and i have around 20% "%wa" value when doing "top" linux command.

But when im monitoring io by "iotop" i see average read rate 150Kb/s and writing around 2Mb/s. Rarelly its writing 20Mb and i seen even 40Mb (rare)

Im curious why there is %wa value so high when disk full writing/reading speed is used from around 20% only according to iotop?

disk is: TOSHIBA DT01ACA200 2TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive Bare Drive - Newegg.com
smartctl -a /dev/sda is without errors.

thx

syg00 · 05-03-2014, 01:51 AM

You seem pre-occupied with iowait - I see two similar current threads.

This is a terrible metric - even when understood, which is rare. Have a read of this thread.

postcd · 05-03-2014, 11:40 AM

sundialsvcs replied to my topic: "...What is the problem that you are trying to address? Where and why and what does it hurt?"

------------

my reply: Problem is high %wa value in "top" command and from time to time slowness of responses in VPS commands and even website loading. Please advice me further on how to debug cause of high %wa, io of mysql process