If you reach on resource limits on your virtual server under the use of virtualization solution OpenVZ / Virtuozzo, a result can be e.g. the non-access to your virtual server or a running process on this server. 

Please check the resource utilization of the virtual server with the following command:

cat /proc/user_beancounters

Only these values are relevant for your virtual server. Most programs for virtualization, e.g. storage usings, are made for dedicated servers and can deliver inaccurate or completely faulty values in certain circumstances.

You get a table by the command above. In the right column you find the so-called "Failcounts". If a counter > 0 in this column, the line value for your limit has been exceeded. These limits match the real hardware values of a physical dedicated server.

If a limit is exceeded, you have the following possibilities:

a) deactivate resource demanding services

b) optimize your services to run with less resources

c) make an upgrade on virtual hardware (e.g. plan upgrade)