Dynamic management of destage tasks in a storage controller

A method of destaging data form a cache and a non-volatile storage (NVS) via a device adapter to each of a plurality of storage devices, comprising:

• adaptively varying a destage rate of data from cache to maintain a desired total occupancy of the NVS and increase data throughput to the plurality of storage devices subject to a constraint that a device occupancy of the NVS related to each said storage device is no greater than a maximum device occupancy of the NVS, wherein a total maximum allocation of available space in the NVS to all the storage devices exceeds one hundred percent of available space in the NVS, said destage rate adaptively varied by setting the destage rate to a maximum if the total occupancy of the NVS exceeds a maximum total occupancy of the NVS, setting the destage rate to a minimum if the device occupancy of the NVS is less than a minimum device occupancy of the NVS and else setting the destage rate to an nominal value based on a ratio of the current device occupancy of the NVS;
• and
• if the destage rate is set to the nominal value,
• checking a current stage activity on said storage device;
• if current stage activity is less than a first threshold, incrementing the destage rate from the nominal value and if the current stage activity is greater than a second threshold, decrementing the destage rate from the nominal value;
• checking a current utilized bandwidth of the device adapter;
• incrementing the destage rate if the current utilized bandwidth is less than a third threshold and decrementing the destage rate if the current utilized bandwidth is greater than a fourth threshold;
• and
• destaging data from the cache to the storage device at the adjusted destage rate and discarding the destaged data from the NVS.

A system for destaging data from a cache and respective portions of a non-volatile storage (NVS) via a device adapter to each of a plurality of storage devices, each said storage device having an associated current storage occupancy in the NVS, comprising:

• at least one processor in communication with the cache and NVS and the plurality of storage devices, wherein for each said storage device the processor is adapter for:
• adaptively varying a destage rate of data from cache according to a current storage occupancy of the NVS associated with the storage device to set a nominal value for the destage rate;
• checking a current stage activity on said storage device;
• adaptively adjusting the destage rate from the nominal value according to current stage activity on the storage device, said destage rate incremented if the current stage activity is less than a first threshold and decremented if the current stage activity is greater than a second threshold;
• and
• destaging data from cache to the storage device at the adjusted destage rate and discarding the destaged data from the portion of the NVS associated with the storage device.

A computer program product for facilitating destaging data from a cache and respective portions of a non-volatile storage (NVS) via a device adapter to a plurality of storage devices, each said storage device having an associated current storage occupancy in the NVS, the computer program product comprising a non-transitory computer-readable storage medium having computer-readable program code portions stored therein, the computer-readable program code portions comprising:

• a first executable portion for adaptively varying a destage rate of data from cache according to a current storage occupancy of the NVS associated with each said storage device to set a nominal value for the destage rate to each said storage device;
• a second executable portion for checking a current stage activity on each said storage device;
• a third executable portion for adaptively adjusting each said destage rate from the nominal value according to the current stage activity on each said storage device, said destage rate incremented if the current stage activity is less than a first threshold and decremented if the current stage activity is greater than a second threshold;
• and
• a fourth executable portion for destaging data from cache to the storage device at the adjusted destage rate and discarding the destaged data from the portion of the NVS associated with the storage device for each said storage device.