Unstable server - high CPU wait time

Server: Ubuntu server 18.04 64-bit
Memory: 1.5 GB
Swap: 1.5 GB
Hard disk: 70 GB (80% used)
ISPConfig version: 3.1.13

Recently my server has become unstable: individual services frequently restart, especially amavis, clamd, apache2 and PHP-FPM, and sometimes the whole server becomes unresponsive or reboots spontaneously. I have not made any major changes that might account for this, although I do update the packages regularly.

The top line of the monit webpage now frequently shows CPU usages like this: 7.3%us, 7.1%sy, 75.2%wa
If I understand this correctly, the very high wait percentage indicates a problem with disk I/O.

I have also noticed frequent occurrences of the following message in the HTML5 Serial Console:
A stop job is running for /dev/xvda2 (56s / no limit)
xvda2 is the swap partition. As there is 'no limit' on the failing stop job (why?), the server has to be manually restarted.

Do these symptoms imply a problem with the swap partition, as I suspect? How should I troubleshoot it? I'd be very grateful for any help.

 

It's a professionally hosted XenPV VPS, so I don't think smartmontools would produce meaningful results, would it? I don't have access to the host machine, although I could raise a support ticket in case the host hard drive has a problem. That seems unlikely, though, as I would expect them to be running diagnostic tools and to be aware of disk errors.

 

Is the host running out of memory? Is swap full?

 

As it's a professional VPS, hosted on a large server, it's highly unlikely that the host is running out of memory, as this would affect all the VPSs on the host and they would have to fix it immediately.

Swap does get quite full at times, occasionally reaching over 80% for a short time, but I haven't seen it reach 100% and it certainly isn't full when I'm seeing the high CPU wait percentages.

Perhaps I should try disabling swap, formatting it with mkswap (keeping the same UUID) and enabling it again?

 

Thanks, Till. I think all the VPSs on the host are limited in the resources they can use. However, I will open a support ticket and see what they advise.

Meanwhile, do you think my suggestion of disabling swap, formatting it with mkswap and enabling it again is worth a try?