CirrusGrid uses Virtuozzo Containers for supporting the largest amount of applications on a single physical server. This is achieved by using operating system-level virtualization. Container-based virtualization helps to slice hardware nodes on smaller containers and get very high density. The containers located on the Hardware Nodes are independent Linux machines on CentOS (other versions of Linux are also supported).
Container-based virtualization guarantees the highest application density and maximum utilization of server resources. Since each container is fully isolated, they are highly secure and provide maximum uptime. This isolation prevents the neighboring containers from behaving badly, for example stealing resources from another. Each environment with provisioned containers gets complete privacy and becomes unavailable for all other users.
Better density and a higher utilization rate is gained with a help of memory deduplication mechanism. This mechanism collects statistics to determine which files are the most frequently accessed by containers. The most commonly used files are put in cache. If a container needs to access a commonly used file, it can go straight to the cache instead of the disk. This improves performance by reducing the number of I/O operations.
CirrusGrid’s hibernation feature delivers even better utilization of cluster resources. Optimal use of resources is achieved by suspending non-active containers and returning released resources back to the cluster.
Because they are in sleep mode, hibernated containers do not consume resources (only disk space). As a result you save money while your containers are in hibernate mode. If applications are needed again the platform returns them to a running state again in just a few seconds.