Patent ID: 7395377
Filing Date: 2008-07-01
Classification: G06F

Abstract:
1. A method of determining when to destage write data from a fast, non-volatile storage (NVS) of a computer system from an upper level of storage to a lower level of storage in said computer system, said method comprising: adaptively varying a destage rate of said NVS according to a current storage occupancy of said NVS; maintaining said high threshold level for said NVS; maintaining a low threshold level that is set to be a predetermined fixed amount below said high threshold level; setting said destage rate of said NVS to be zero when the NVS occupancy is below said low threshold level; setting said destage rate of said NVS to be maximum when said NVS occupancy is above said high threshold level; linearly increasing said destage rate of said NVS from zero to maximum as said NVS occupancy goes from said low threshold level to said high threshold level; maintaining a desired occupancy level for said NVS; maintaining a max occupancy observed variable for said NVS; initializing said high threshold level to be equal to a desired occupancy level, wherein said high threshold level is constrained to never exceed said desired occupancy level; if said NVS occupancy drops below a current high threshold level, and if said max occupancy observed variable is greater than said desired occupancy level, decrementing and backing-off said high threshold level by a positive difference between said max occupancy observed variable and said desired occupancy level; and resetting said max occupancy observed variable.