High %wa , but iotop shows low disk usage


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 2Mb/s and writing around 500Kb/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: http://www.newegg.com/Product/Product.aspx?Item=N82E16822149407
smartctl -a /dev/sda is without errors.


if I’m understanding your question…

If I’m right (and I might not be :wink: ), %wa is a percentage of CPU being used by a process that’s sleeping whilst awaiting I/O

I gather it’s probably rsync doing a lot of waiting because data traversing the network is much slower than plain disk I/O

or am I misunderstanding your question ?

Hi, you understand properly what i meant.

I killed rsync before around 45 minutes and now when watching iotop, biggest i/o eaters are a few processes of mysql:

mysqld --basedir=/usr --datadir=/var/lib/mysql --plugin~d-file=/var/lib/mysql/hostname.mydomain.com.pid
mysqld --basedir=/usr --datadir=/var/lib/mysql --user=m~kip-external-locking --socket=/var/lib/mysql/mysql.sock
mysqld --basedir=/usr --datadir=/var/lib/mysql --user=m~kip-external-locking --socket=/var/lib/mysql/mysql.sock

interesting is that iotop gives me impression that around 20% only of disk transfer speed is used :frowning:
(i mean i see like Write speed average 3Mb/s while maximum hdd speed is around 45Mb/s i think

the %wa sits still on %17 , normal should be 0-5%, i experience little slowdowns as server delays requests because of high i/o