Multiple I/O processor system

In a processing system including at least one CPU which issues I/O job function requests, a main memory and a plurality of I/O devices, a system for handling the I/O job function requests comprising:

• at least two I/O processor means for performing I/O job functions including selecting paths and managing I/O devices;
• I/O controller means, coupled to the CPU, for allocating received I/O job function requests between the two I/O processor means, wherein one of the I/O processor means includes the I/O controller means;
• and
• data structure means for storing I/O device information used during allocation of the I/O job function requests,
• wherein the I/O controller means receives an I/O job function request from the one CPU, and responsive to the device information in the data structure means assigns the I/O job function to one of the I/O processor means.

In a processing system including at least one CPU which issues I/O job function requests, a main memory and a plurality of I/O devices, a system for handling the I/O job function requests comprising:

• at least one slave I/O processor (sIOP) means, separate from the CPU, for performing I/O job functions including selecting paths and managing I/O devices;
• master I/O processor (mIOP) means, separate from the CPU, for both performing I/O job functions including selecting paths and managing I/O devices, and allocating received I/O job function requests between the sIOP means and the mIOP means;
• and
• data structure means for storing information used during allocation of I/O job function request,
• wherein the mIOP, being coupled to the CPU, receives an I/O job function request from the at least one CPU, and based on the information in the data structure means either assigns the I/O job function to the sIOP means or the mIOP means.

In a processing system including at least one CPU which issues I/O job requests, a main memory, at least two I/O processors, and a plurality of I/O devices each assigned to be serviced by one of the I/O processors, a process for substantially evenly distributing the I/O jobs among the I/O processors, comprising the steps of:

• a) generating a value representing the number of I/O jobs handled by each I/O device during a predetermined time interval;
• b) calculating a total number of I/O jobs for each I/O processor as a sum of the value generated in step a) for each I/O device which is assigned to the I/O processor, wherein at least a highest total and a lowest total are obtained;
• c) calculating a difference value as the difference between the I/O processors with the highest and lowest totals from step b) for the I/O processors;
• d) comparing the difference value in step c) with a predetermined maximum allowable difference value;
• e) if the difference value in step c) is greater than a predetermined maximum allowable difference value,
• (i) reassigning from the I/O processor having the highest total in step b) to the I/O processor having the lowest total in step b) the I/O device with the value from step a) which is closest in value to the difference value from step c) divided by two, and
• (ii) repeating step e) using the remainder of the difference value from step c) as the difference value if the total number of I/O jobs reassigned is less than one-half the difference value from step c);
• f) resetting the I/O job counts for the I/O devices.

In a processing system including at least two I/O processors which both handle I/O job requests, and wherein one of the I/O processors also allocates I/O job requests between the at least two I/O processors, a process for detecting a failed non-allocating (slave) I/O processor and replacing that non-allocating (slave) I/O processor with the allocating (master) I/O processor to enhance system resiliency, comprising the steps of:

• a) issuing a check-in message from the allocating I/O processor to one of the non-allocating processors;
• b) detecting that the non-allocating I/O processor has not responded within a predetermined time period;
• c) disabling the non-responding, non-allocating I/O processor from the processing system;
• d) accessing any I/O job requests that the non-responding, non-allocating I/O processor had not handled;
• and
• e) re-allocating the any I/O jobs the non-responding, non-allocating I/O processor had not handled to another I/O processor in the processing system.

In a processing system including at least two I/O processors which both handle I/O job requests, and wherein one of the I/O processors also allocate I/O job requests between the two I/O processors, also including a console connected to each of the I/O processors with access to local memories of the I/O processors, a process for replacing the allocating (master) I/O processor with a non-allocating I/O processor to enhance system resiliency, comprising the steps of:

• a) detecting that the allocating I/O processor is no longer functioning properly;
• b) disabling the allocating I/O processor from the processing system;
• c) retrieving, by way of the console, any I/O job requests which the allocating I/O processor had not handled and any information in the local memory of the allocating I/O processor needed for allocating the I/O job requests;
• d) loading, by way of the console, the data retrieved in step c) into the non-allocating I/O processor;
• and
• e) restarting the processing system such that the non-allocating I/O processor is now an allocating processor.