Managing IO path bandwidth

A storage system coupled to a host by a switch, wherein a plurality of IO paths are defined between the host and the storage system across the switch, each IO path having a defined bandwidth threshold, the storage system comprising executable logic that implements a method including:

• a first host port of the host logging into a first storage system port of the storage system, wherein the first host port and the first storage system port denote a first IO path that includes the first storage system port, wherein the first IO path includes a physical link between a first switch port of the switch and the first storage system port of the storage system;
• in response to said first host port logging into the first storage system port, setting a first defined bandwidth threshold for the first IO path;
• and
• the storage system monitoring communications received at the storage system from the switch, wherein said monitoring performed by the storage system includes:
• receiving a first notification at the storage system from the switch, wherein the first notification is generated by, and originates from, the switch and indicates there is congestion on the physical link between the first switch port of the switch and the first storage system port of the storage system, wherein the storage system receiving the first notification from the switch exposes one or more logical devices of the storage system to the host over the first IO path including the physical link, wherein each of the logical devices is provisioned from non-volatile physical storage of one or more physical storage devices of the storage system;
• responsive to the storage system receiving the first notification that is generated by and originates from the switch, determining, by the storage system, that there is congestion on the physical link between the first switch port of the switch and the first storage system port of the storage system;
• in response to said determining by the storage system that there is congestion on the physical link, the storage system reducing the defined bandwidth threshold for each of the plurality of IO paths that includes the first storage system port, wherein the plurality of IO paths include the first IO path and wherein said reducing includes the storage system reducing the first defined bandwidth threshold for the first IO path that includes the first storage system port;
• receiving a notification at the storage system from the switch indicating that the physical link is faulty, wherein the notification regarding the physical link being faulty is generated by, and originates from, the switch;
• and
• responsive to receiving the notification indicating that the physical link is faulty, performing fault processing by the storage system, wherein a logical device of the plurality of logical devices is exposed by the storage system to the host over the first IO path which includes the first storage system port and which includes the physical link that is faulty, and wherein said fault processing includes:
• determining whether the logical device, which is exposed to the host over the first storage system port of the physical link that is faulty, is exposed to the host by the storage system over a first plurality of paths including the first IO path and at least one additional IO path between the host and the storage system;
• determining whether the host supports multi-path processing and includes a multi-path driver that, for each I/O directed to the logical device exposed to the host over the first plurality of paths, selects a particular one of the first plurality of paths to be used for sending said each I/O from the host to the storage system;
• responsive to determining that the host does not support multi-path processing and does not include the multi-path driver, determining not the reduce the first defined bandwidth threshold for the first IO path;
• and
• responsive to determining that the logical device is not exposed to the host over the first plurality of paths including the first IO path with the physical link that is faulty at least one additional IO path between the host and the storage system, determining not to reduce the first defined bandwidth threshold for the first IO path.

For a system including a storage system coupled to a host by a switch, wherein a plurality of IO paths are defined between the host and the storage system across the switch, each IO path having a defined bandwidth threshold, non-transitory computer-readable media having software stored thereon comprising:

• executable code that, for a first host port of the host, logs into a first storage system port of the storage system, wherein the first host port and the first storage system port denote a first IO path that includes the first storage system port, wherein the first IO path includes a physical link between a first switch port of the switch and the first storage system port of the storage system;
• executable code that, in response to said first host port logging into the first storage system port, sets a first defined bandwidth threshold for the first IO path;
• and
• executable code that causes the storage system to perform monitoring of communications received at the storage system from the switch, wherein said executable code that causes the storage system to perform said monitoring includes:
• executable code that receives a first notification at the storage system from the switch, wherein the first notification is generated by, and originates from, the switch and indicates there is congestion on the physical link between the first switch port of the switch and the first storage system port of the storage system, wherein the storage system exposes one of more logical devices of the storage system to the host over the first IO path including the physical link, wherein each of the logical devices is provisioned from non-volatile storage of one or more physical storage devices of the storage system;
• executable code that, responsive to the storage system receiving the first notification that is generated by and originates from the switch, causes the storage system to determine that there is congestion on the physical link between the first switch port of the switch and the first storage system port of the storage system;
• executable code that, in response to the storage system determining that there is congestion on the physical link, causes the storage system to reduce the defined bandwidth threshold for each of the plurality of IO paths that includes the first storage system port, wherein the plurality of IO paths include the first IO path and wherein the executable code that causes the storage system to reduce the defined bandwidth threshold for each of one or more of the plurality of IO paths includes the storage system reducing the first defined bandwidth threshold for the first IO path that includes the first storage system port;
• executable code that receives a notification at the storage system from the switch indicating that the physical link is faulty, wherein the notification regarding the physical link being faulty is generated by, and originates from, the switch;
• and
• executable code that, responsive to receiving the notification indicating that the physical link is faulty, performs fault processing on the storage system, wherein a logical device of the plurality of logical devices is exposed by the storage system to the host over the first IO path which includes the first storage system port and which includes the physical link that is faulty, and wherein said executable code that performs said fault processing includes:
• executable code that determines whether the logical device, which is exposed to the host over the first storage system port of the physical link that is faulty, is exposed to the host by the storage system over a first plurality of paths including the first IO path and at least one additional IO path between the host and the storage system;
• executable code that determines whether the host supports multi-path processing and includes a multi-path driver that, for each I/O directed to the logical device exposed to the host over the first plurality of paths, selects a particular one of the first plurality of paths to be used for sending said each I/O from the host to the storage system;
• executable code that, responsive to determining that the host does not support multi-path processing and does not include the multi-path driver, determines not the reduce the first defined bandwidth threshold for the first IO path;
• and
• executable code that, responsive to determining that the logical device is not exposed to the host over the first plurality of paths including the first IO path with the physical link that is faulty at least one additional IO path between the host and the storage system, determines not to reduce the first defined bandwidth threshold for the first IO path.