Basically we provide virtual server with seemingly infinite large disk storage.
The file systems of a project ara always only available on the virtual server of the project. Our SAM-FS server which of cause can see all file systems is not reachable for users.
Direct access to the tape libraries is only available for our SAM-FS server.
On the virtual server we give access with the role of administrator for the project manager if this is requested.
The tapes are strictly assigned to a project. A mixture of data from different projects on one tape is impossible.
Structure of usage
The following figure explains the structure of usage for the Hirarchical Storage System (HSM) within Projects of long-term storage.
Over IP protocols the hosts of the project partners have access to a virtual server provided by us. This server has access to a file system that is located on a disk storage at ZIB.
Per file system a fixed area of disk space is allocated for exclusive use by the project. The technical specification and the size of the disk space depends on the requirements of the project. Anyhow the disk storage is attached to the central disk storage at ZIB over fibre channel.
The disk storage is used only as cache for acceleration of access and never will be become full.
Our server have access to all file systems of the project partners. The concurrent access of the server and the virtual project server to one file system is enabled by QFS (Quick File System).
According our rules the SAM-FS (Storage and Archive Manager) on our server copies new and changed files as two copies to two independant tape libraries. For each project two pools of tapes are reserved for that purpose.
If disk space becomes full data of some files will be removed from disk. Because the inodes remaining proper information services are furthermore seeing the files. If such a file is opened SAM-FS automatically restores the data from tape to disk.
The work of creating copies, releasing and restoring data is automatically done without interaction by users. The state of a file can be inquired by users. If there is the need these processes can be manual initiated by users on the virtual project server.