InveStore v4 creates volume sets that use Intelligent Spanning capabilities. This provides application control of the volume set size. At format time, the application can choose one of the following two options:
· The volume set size is permanently set which prevents it from ever being grown.
· The volume set size is programmed to grow automatically. When the volume set runs out of space, InveStore will automatically take any blank disk within the library and add it to the volume set. An upper limit to such a volume set can be specified to prevent it from becoming too unwieldy. The order in which the disk surfaces of the volume set are written, is fully configurable by the application.
· Contiguous order writing instructs the system to write to side A followed by side B of each disk. This works well with single drive libraries since only one surface can be accessed at a time.
· Staggered order instructs the system to write to side A of each disk in the volume set followed by side B. This approach works best for multi-drive libraries, as more data can be accessible at any given time since only one side of a disk can be accessed in the drive.
Intelligent Spanning automatically clusters all of the data within a subdirectory to a single surface whenever possible. The application can specify that the system reserve a given amount of space for each subdirectory created. If this space is not available, the directory and all its files are written to the next available surface.
Intelligent Spanning reserves a configurable amount of space for file updates on each surface. This space is not used for new files. This feature helps prevent files from being spread across multiple surfaces, as time goes on, and greatly reduces the severe performance degradation that volume sets incur over time.
Intelligent Spanning also uses an automatic copy feature when a given file is updated and there is no space left on that surface. If the fixed size is below a configurable threshold, the entire file will be copied to a new surface and the update handled there. This feature also reduces the amount of file fragmentation across surfaces.
Intelligent Spanning incorporates a number of other features to help reduce the amount of system administration required to handle volume sets including the ability to UNMOUNT and remove the least recently used volume set or cartridge within the volume set.
This allows the administrator to free up space within the library without having to manually track usage and determine what files and directories exist on a given surface. The data allocation for any file is also viewable, which is useful in determining whether a file has become fragmented across surfaces.
Note: The Volume Sets level is discussed in detail in the Help section on Volume Sets.