Storage control system and method

A storage control method, which can be realized by a storage system, which comprises a storage control system, and an external storage subsystem, which is a storage subsystem that exists externally of said storage control system, said storage control method comprising the steps of:

• receiving a first I/O command for a certain object, of one or more objects to which a plurality of external storage devices, being a plurality of storage devices provided in said external storage subsystem, is respectively mapped;
• attempting either to acquire data in accordance with said received first I/O command, or to secure a storage area for this data in the memory area corresponding to an element of the communication path to the external storage device mapped to said certain object, in a memory, which is a memory capable of storing data either written to an external storage device or read from an external storage device, and which has two or more memory areas respectively allocated to elements of two or more communication paths connecting said storage control system and said plurality of external storage devices;
• sending the I/O result, which is the processing result of said first I/O command, to a transmission source of this first I/O command if this attempt succeeds;
• sending a second I/O command for carrying out access in accordance with said first I/O command to the external storage subsystem having said mapped external storage device, and thereafter, sending the result of said I/O processing to said transmission source if said attempt fails;
• monitoring the respective communication states of said two or more communication paths;
• and
• allocating, as a result of monitoring, more memory area capacity to the element of the communication path with the poorer communication state.

A storage control system of a storage system, which comprises an external storage subsystem, which is a storage subsystem that exists externally of said storage control system, said storage control system, and a host of said storage control system,

• wherein when said external storage subsystem has one or more first communication ports capable of communicating with said storage control system, and a plurality of external storage devices, which is a plurality of storage devices, and when said host is constituted so as to issue to said storage control system a first I/O command for either reading data or writing data, said storage control system comprises:
• a second communication port capable of communicating with said host;
• one or more third communication ports capable of communicating with one or a plurality of external storage subsystems;
• one or more objects to which said plurality of external storage devices is respectively mapped;
• a memory, which is a memory capable of storing data either written to an external storage device or read from an external storage device, and which has two or more memory areas respectively allocated to elements of two or more communication paths connecting said storage control system and said plurality of external storage devices;
• an I/O processor, which receives a first I/O command for a certain object of said one or more objects, and attempts either to acquire data in accordance with this first I/O command, or to secure a storage area for this data in the memory area corresponding to the element of the communication path to the external storage device mapped to said certain object, and if this attempt succeeds, sends the I/O result, which is the processing result of said first I/O command, to a transmission source of this first I/O command, and if said attempt fails, sends a second I/O command, for carrying out access in accordance with said first I/O command, to the external storage subsystem having said mapped external storage device, and thereafter, sends the result of I/O processing to said transmission source;
• a monitor for monitoring the respective communication states of said two or more communication paths;
• and
• an allocating portion for allocating more memory area capacity to an element of a communication path with a poorer communication state according to the result of monitoring,
• wherein said communication path element is at least one of a first communication port, a third communication port, or an external storage device, which belongs to the communication path;
• said communication state is a statistic of measured values of a plurality of response times of second I/O commands issued to the communication path;
• said monitor issues to a certain communication path a dummy second I/O command, which is different from a second I/O command for access in accordance with said first I/O command, and measures the response time by said certain communication path by receiving the response of this dummy second I/O command;
• said statistic is either the average value of measured values of said plurality of response times, or the range of response time measured values, of a plurality of ranges of response time measured values, in which the number of obtained response time measured values is the greatest;
• the total memory capacity capable of being allocated to the elements of said two or more communication paths is fixed;
• and
• said allocating portion allocates a high ratio of memory area capacity to an element for which said statistic of the communication path is greater than a prescribed value, allocates a low ratio of memory area capacity to an element for which said statistic is less than a prescribed value, and determines the memory area capacity to be allocated to the elements of said respective communication paths based on the ratio of memory capacity of the elements of said respective communication paths and said total memory capacity.