Performance problems %util=100 with no load

eliaswa · 02-03-2012, 03:51 AM

We have an ubuntu server running on a VPS (CityCloud).
We use it as a database server (SQL Anywhere with MobiLink synchronization) and an apache web server for an administration interface.
Usually there are 15-20 server processes running, but the load is very low, most of the time there are NO db requests and NO synchronization going on, and NO web requests. But the response times are often very bad for example when doing work in a ssh terminal or making a http request.
iostat show this all the time (typically):

Code:

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0.17    0.00    1.25   67.25    0.00   31.33

Device:         rrqm/s   wrqm/s     r/s     w/s    rMB/s    wMB/s avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00    19.67    2.00    2.67     0.01     0.09    42.29    11.41 6409.29 214.29 100.00
scd0              0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00

iotop shows that most of the time total DISK READ and DISK WRITE is 0.00.

What's going on?

syg00 · 02-03-2012, 04:15 AM

Go beat up on your service provider.
You're doing some (not much) write I/O, but it's taking forever to complete.
I'd guess you are hosted on a shared disk, and being affected by a heavy user (guest) elsewhere.

eliaswa · 02-10-2012, 05:45 AM

Thank you!
The problem was at the service provider, but not because of another heavy user. They had some problem with the disk nodes which is resolved now.