Resource management using openVZ
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Resource allocation can be done using 'vzctl set ' command dynamically. The changes can be made persistent by using '--save' option with 'vzctl set' command. The permanent changes are saved in configuration file '/etc/vz/conf/<container_id>.conf' file
I/O priorities for containers
I/O priorities can be set using:
vzctl set <container_id> --ioprio {[0-7]} --save
Here, 0 is higher or better than 7. Default I/O priority is 4. (Read http://wiki.openvz.org/I/O_priorities_for_VE for more details).
Disk space for containers
Disk space allocated to a container can be set using:
vzctl set <container_id> --diskspace <num1>:<num2> --save
Example: 'vzctl set 101 --diskspace 6G:7G --save' to set the space and 'vzctl exec 101 df -h' to verify the setting.
Just configuring diskspace may not be enough. It is recommended to configure inode limits as well. To configure inode limits use:
vzctl set <container_id> --diskinodes <num1>:num2> --save
To enable/disable quota for a particular container use:
vzctl set <container_id> --diskquota {yes|no} --save
Read http://wiki.openvz.org/Disk_quota for more details
Verify whether current resources allocated to container are enough
One can verify whether current resources allocated to a container are enough by using:
less /proc/user_beancounters
The output includes various details like current resource utilization of container, maximum resource utilization for given container, various resource limits etc. A very important column titled 'failcnt' indicates number of times a container tried to access a particular resource and was denied due to resource limits. Now if this number if high for a given parameter for a specific container than it indicates that the container needs more resources of that type for it to function properly. Thus, /proc/user_beancounters can provide very useful feed-back related to resource allocation (crunch/abundant) for various containers.
Most of the things in this page are learned from http://wiki.openvz.org/Resource_management
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