OpenVZ containers often appear to use a lot more memory than they actually are. This is because OpenVZ accounts for memory differently than other virtualizations.
In OpenVZ, the total memory (RAM) usage is divided into two types: User memory and Kernel memory. User memory is the memory used by your applications, while Kernel memory is used by the system to perform operations.
OpenVZ also has a feature called ‘burstable memory’, allowing your container to use more than the guaranteed amount of memory temporarily, assuming it’s available on the host.
However, there are also other reasons why your OpenVZ server memory could be getting exhausted:
1. If you’re running a lot of processes or heavy applications, they could be using up all the available memory.
2. If you’re not properly optimizing or configuring your applications, they could be using more memory than necessary.
3. If there’s a memory leak in one of your applications, it could gradually eat up all your memory.
Keep in mind also that the ‘free -m’ command is not reliable in an OpenVZ environment for checking memory usage. A better method is to use the ‘vzcalc’ or ‘vzfree’ commands. Or you can check from the host node itself for accurate information.
