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I'm new to managing servers, and I've run into something that's stumped me. I received a warning from my VPS provider informing me that my load usage was very high. I hadn't run into this problem before, so I attempted to look into it. Unfortunately I haven't been able to figure out why this is the case after quite a bit of research.

The server is, I believe, OpenVZ, with plenty of RAM to spare (2 GB) and a decent processor with a SSD. I've shut down nearly every process that I could imagine that might be an issue besides apache. I've inspected my top/htop output very carefully and I can't detect anything unusual. But notice the load average. It should be around 0 with this level of CPU usage, right?

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I was wondering if it was maybe something to do with disk usage, but since this is OpenVZ apparently I can't use a tool like atop to determine more information about disk activity.

How can I debug this further? Thanks!

Yep
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  • Use `iotop` or similar to look at disk usage - did you review crontab and the /etc/cron.* to ensure something in there isn't hitting IO hard? – albal Sep 13 '15 at 10:48
  • @albal: Thanks for your comment. There's nothing abnormal in any user's crontab; I checked them all. I will try to look further into IO. – Yep Sep 14 '15 at 09:23
  • `iotop` shows really nothing at all is using much of the disk, which is really quite unfortunate since I was hoping I would find the solution to my problem right there. Now I'm not sure what could be causing this. – Yep Sep 14 '15 at 09:30
  • You can show IO with htop as well fish around the settings, also show advanced CPU usage, see if shows a core or two on full grey bars but no process using that much (as it is now in your screen), I've found it usually is something flushing stuff to disk and having a very high IO latency on the virtual host – Recct Oct 07 '15 at 11:09

2 Answers2

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As you're in a VPS environment:

Did you ever consider that the load is coming from the host? Maybe you have only 2 virtual CPU cores assigned and the host system is overcommitted or completely exhausted. Therefore your load is rising because any small request is taking a long time. This would explain the sluggish behaviour.

You should talk to your VPS Provider about this.

HBruijn
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JinnFox
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There are situations where you observe a high load average combined with low CPU usage, see this discussion for some possible reasons. The Wikipedia article on load is also pretty informative.

The problem is, some of these situations are harmless (I used to manage an Informix server on HPUX where the load average was equal to the number of configured Informix VPs, even when idle), when it's some kind of IO related it may slow processing down quite a lot - see the example in the linked article.

If the system "feels" responsive I wouldn't worry too much, but as you have server metrics available (I see you have sealion installed), I'd have a look at IO related values, it may help you understand your system better and avoid surprises later on.

Community
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fvu
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  • Thanks for your response! Unfortunately the server does not feel responsive like it used to. In fact, it's quite sluggish. That's why I'm suspecting something is not right. – Yep Sep 14 '15 at 09:22