Abstract: A method and apparatus, for a system having a plurality of host computers and a memory system having a disk controller with at least one mass storage device having a plurality of logical volumes, provide for write protecting the logical volumes at the controller port level. The method features changing the write protect status of one or more logical volumes, on a port level basis, in response to a first host request to change a write protect status; writing a write protect status message to a memory associated with the controller channel directors; polling, from each channel director, the memory for an unread write protect status messages; and preventing, at, for example, the channel director port level, a host connected to the channel director from writing to a protected logical volume which is write protected from that host or host port. The write protect status of that channel director, for that logical volume, remains in effect until the write protect condition for that volume has been reset.

Abstract: The invention relates to a disk drive controller system having redundant operations spread between at least two SCSI adaptors connected to a SCSI bus. At least one host computer is also connected to the SCSI bus. If one of the SCSI adaptors fails, the other SCSI adaptor connected to the bus, upon detecting the failure, takes over for the devices serviced by the failing SCSI adaptor. A special termination connection, in which one SCSI adaptor terminates the SCSI bus while the other SCSI adaptor does not, is provided for implementing the invention. A defined process enables the detecting SCSI adaptor to take over for the failed SCSI adaptor and for the failed SCSI adaptor to thereafter return to normal operation.

Abstract: A method of managing a storage system is provided which allows each host of connected to a storage system supporting multiple hosts to view the identification information assigned to the storage devices by the respective hosts. The method includes providing a command which allows a host to write identification information to an area on the disk drives controlled by the host which was previously reserved for use by the storage system. In addition to writing the data to the physical storage device, execution of the command also causes the identification information to be written to an area in global memory which holds information about each of the storage devices in the storage system. Since the information is stored in a global memory, each host my access the information. Using a second command provided, any host may read the information in global memory and thus learn the identification assigned by other hosts.

Abstract: A method and apparatus, operating in a system having a plurality of host computers and memory system having a disk controller with at least one mass storage device having a plurality of logical volumes, provide for write protecting the logical volumes. The method features writing, in response to a first host, a write protect message to a memory associated with the controller channel directors; polling, from each channel director, the memory for new write protect messages; and preventing, at, for example, the channel director level, a host connected to the channel director from writing to a protected logical volume which is the subject of the write protect message. The write protect status of that channel director, for that logical volume, remains in effect until the write protect condition for that volume has been reset.