In BS2000, disks are addressed logically via the volume serial number (VSN). Volumes can be operated as:
Public volumes: Public volumes are operated in SF pubsets (Single-Feature pubsets), SM pubsets (System-Managed pubsets) or shared pubsets.
Irrespective of which logical operating mode is in use, the time taken to perform a single data access operation is approximately the same (if the disks are of the same type).
There are, however, serious differences regarding the number of I/O operations to be performed when calling functions which require catalog access. This is due to the differing degrees of complexity with regard to memory management or the co-ordination of multiprocessor operation.
To increase availability, the following operating modes are also provided:
DRV: Dual Recording by Volume: Data mirroring controlled by BS2000 (software product DRV, for details see the "DRV" manual [7 (Related publications)])
Replication: volume-based mirroring for storage systems
Disk mirroring, controlled by the ETERNUS DX/AF and Symmetrix storage systems. In the ETERNUS DX/AF and Symmetrix storage systems, the RAID-1 level is available on the hardware level. Dual data recording takes place without the need for any further software support.