I have subscribed to a VPS offered by a hosting provider. The guaranteed performance 1GB RAM, 1M bandwidth.

But I found that from time to time the websites can be very slow, so slow that it could take more than 30 seconds to load a simple Joomla website. However the website resumed the usual speed after a few minutes.

This created a problem for me when I want to report the performance problem to the hosting provider. They would say to me "see, no problem". Of course there is no problem because the problem is only there for a few minutes , and everything is normal.

This ocassionally-slow problem will bug me a few days later and the cycle repeats.

Any idea how to solve this problem?