Peripheral systems employing multipathing, path and access grouping

A control for a peripheral system having a plurality of peripheral devices and attachable via a plurality of paths to a plurality of hosts for performing peripheral operations commanded by the hosts via peripheral commands sent to said control;

• comprising:
• first means being coupled to said paths for being responsive to a first of said peripheral commands for establishing path group allocations for enabling multipath reconnections of said devices to a said hosts connected to said control unit via paths in said established path group allocation;
• second means being coupled to said paths for being responsive to a second of said peripheral commands for establishing simultaneously existing dynamic plural access groups of permitted allegiances of said peripheral devices to said hosts via one or more of said path groups;
• and
• third means being coupled to said first and second means for limiting said first means established device multipath reconnections in accordance with said second means existing access groups.

A peripheral system attachable to a plurality of hosts via a plurality of paths and having a plurality of peripheral devices;

• including, in combination:
• first means, being coupled to said paths and said devices for electrically indicating a present allegiance of said devices to said hosts via a plurality of groups of said paths, respectively;
• second means being coupled to said paths and said first means to electrically indicate a present set of permitted allegiances of said devices to hosts via a plurality of access groups, some of said paths being in a plurality of said access groups;
• third means being coupled to said paths and said second means for electrically inter-coupling said first and second means for limiting said first means indications for each said device to said second means indications for each said device;
• and
• fourth means being coupled to said paths, said devices and said first means for selectively connecting said devices and hosts via said paths in accordance with said first means indications.

A peripheral system having a control unit connected to a plurality of peripheral devices and having a plurality of means for transferring signals to and from said devices;

• the improvement including in combination:
• the control unit having a plurality of host adaptors, each host adaptor having channel processing control means including chain means for indicating a chain of commands and supervisory control means indicating acceptability of system logic control commands to be received from a host;
• a programmed processor in said control unit electrically connected to said channel processing control means and with a control memory for containing program indicia for requiring said programmed processor to control the peripheral system;
• said control memory stored indicia including:
• a path group control indicia being for enabling said programmed processor to set, alter and disband path groups consisting of predetermined ones of said host adaptors and a one of said devices such that said one device can reconnect to a host via any one of said host adaptors within such path group, said one device selectively owing allegiances to a host via any one of said channel processing control means in a respective path group;
• access group control indicia being for enabling aid programmed processor to set, alter and disband access groups for each of said devices and channel processing control means, each device having but one of said access groups and each access group including one or more of said path groups;
• said path group control indicia being for further enabling said programmed processor to activate a path group for a given device only via a one of said host adaptors receiving a command with a device address that is within its access group;
• and
• said access group control indicia being further for enabling said programmed processor to alter each access group each time said path group control indicia alters a path group.

The machine-implemented method of operating a peripheral system having a plurality of devices selectively connectable to a plurality of hosts via a plurality of paths,

• the automatic steps of:
• assigning said paths to access groups, each said access group consisting of one of said devices and one or more of said paths, assigning some of said paths to a plurality of said access groups,
• reserving one of said devices via one of said paths in a given access group to a host for data processing operations via one or more of said paths as a path group for said one device,
• if said devices being reserved do not have an access group, reserve the device,
• if said devices being reserved have an access group, reserve such said devices only if the said path over which a reservation is being made is included in its respective access group, otherwise refuse the reservation and report an error condition to the reserving host.

The machine-implemented method of operating a peripheral system attachable to a plurality of hosts, said peripheral system having a plurality of control units connected to a larger plurality of devices such that any control unit can operate with any device, and each control unit having plurality of host connection adaptors for providing multiple data paths from said hosts to any one of said devices;

• the automatic steps of:
• in each control unit establishing a table of connections for each said host connection adaptor and for each said device for electrically indicating which of said devices is permitted to communicate through which of said host connection adaptors,
• upon receipt of a given command through a one of said host connection adaptors, changing said indications in said table of connections,
• receiving commands for any of said devices as a sequence of separate chained series of commands, in each said series of commands accepting commands received for a given device by said host connection adaptor indicated in said table of connections as being permitted to handle communications for said device, and
• receiving an additional command indicating, that for commands in the series of commands which includes said additional command, commands will be accepted from the host connection receiving said additional command irrespective of said indications in said table of connections.

The machine-implemented method of operating a peripheral system attachable to a plurality of hosts, said peripheral system having a plurality of control units connected to a larger plurality of addressable devices such that any control unit can operate with any device, and each control unit having another plurality of host connection adaptors for providing multiple data paths to any one of said devices,

• the machine executable steps of:
• in each control unit establishing a table of connections for each said host connection adaptor and for each said device for electrically indicating which of said devices is permitted to communicate through which of said host connection adaptors,
• grouping said host connection adaptors into path groups for communication with one or more devices and indicating said group in said table of connections,
• assigning one or more of said path groups to each device of a second plurality of said devices, said second plurality being not greater than said larger plurality;
• maintaining said table of connections over a sequence of a plurality of chained series of commands, and
• for a given set of commands in a given chained series of commands limiting communications of an addressed one of said devices to a one path while at any other time permitting said one device to communicate with its indicated plurality of paths in a one of said path groups.

The machine-implemented method of operating a peripheral system having a plurality of peripheral devices selectively connectable to a plurality of hosts via a plurality of paths,

• the automatic steps of:
• assigning said devices and paths to dynamically determined access groups of paths such that any device or path can be in none of said access groups, said path can be in one or more of said access groups and one device in each of said access groups,
• changing said access groups from time to time,
• reserving said devices to said hosts via said paths in a plurality of sequences of chained peripheral operations in accordance with said access groups, devices not in any of said groups being accessible via any of said paths while devices in an access group being accessible via any of those paths in the same access groups with reconnection being over any path in a group of such paths within said access groups, respectively, independent of which path in such path group initiated a device operation, respectively, and
• during one chain of peripheral operations for a given device overriding said group operation such that one device communicates via a one of said paths independent of said access groups.