Memory controllers for solid-state storage devices

1. A computer system for controlling operation of an array of non-volatile memory cells comprising cells which are selectively configurable for single-bit and multibit storage, the computer system comprising:

one or more computer processors;

a memory controller;

one or more computer readable storage media; and

program instructions stored on the computer readable storage media, the program instructions being executable by a processing device of the memory controller to cause the memory controller to:

selectively configure the array for operation in a hybrid mode, in which the array comprises both cells configured for single-bit storage and cells configured for multibit storage, and a multibit mode in which all cells in the array are configured for multibit storage;

dynamically switch between the hybrid mode and multibit mode configurations of array corresponding to the array capacity-usage traversing a defined threshold level associated with enhancing an endurance of the array;

prior to operation of the array, defining the threshold level in dependence on a set of system parameters for the array, the parameters indicating information selected from the group consisting of:

raw cell endurance in the single-bit mode and multibit mode;

size of the array;

workload-type for the array;

one of a static-hybrid mode, in which a ratio of single-bit and multibit cells is static, and a dynamic-hybrid mode, in which the ratio is dynamically determined, for operation of the array in the hybrid mode; and

whether write-heat segregation is enabled for operation of the array in the hybrid mode.

2. The computer system of claim 1 , wherein the threshold level is defined as a capacity-usage level to transition between the hybrid mode and multibit mode based on array-endurance.

3. The computer system of claim 1 , further comprising program instructions, stored on the computer readable storage media for execution utilizing the memory controller, to:

monitor workload-type during operation of the array; and

dynamically define the threshold level in dependence on the workload-type.

4. The computer system of claim 1 , further comprising program instructions, stored on the computer readable storage media for execution utilizing the memory controller, to:

monitor workload-type during operation of the array; and

dynamically define the threshold level in dependence on the workload-type.

5. The computer system of claim 1 , further comprising program instructions, stored on the computer readable storage media for execution utilizing the memory controller, to:

control operation of the array in accordance with the set of parameters.

6. The computer system of claim 1 , further comprising program instructions, stored on the computer readable storage media for execution utilizing the memory controller, to:

during operation of the array in the hybrid mode, preferentially write data to single-bit cells of the array; and

move data from single-bit to multibit cells, freeing storage capacity in the single-bit cells.

7. The computer system of claim 1 , further comprising:

a storage device; and

the storage device comprising an array of non-volatile memory cells, comprising cells which are selectively configurable for single-bit and multibit storage.

8. The computer system of claim 7 , wherein the array comprises flash memory cells.

9. The computer system of claim 8 , wherein the flash memory cells are selectively configurable for single-bit and 4-bit storage.

10. A method for controlling operation of an array of non-volatile memory cells comprising cells which are selectively configurable for single-bit and multibit storage, the method comprising:

a memory controller selectively configuring the array for operation in a hybrid mode, in which the array comprises both cells configured for single-bit storage and cells configured for multibit storage, and a multibit mode in which all cells in the array are configured for multibit storage;

the memory controller dynamically switching between the hybrid mode and multibit mode configurations of array corresponding to the array capacity-usage traversing a defined threshold level associated with enhancing an endurance of the array;

prior to operation of the array, the memory controller defining the threshold level in dependence on a set of system parameters for the array, the parameters indicating information selected from the group consisting of:

raw cell endurance in the single-bit mode and multibit mode;

size of the array;

workload-type for the array;

one of a static-hybrid mode, in which a ratio of single-bit and multibit cells is static, and a dynamic-hybrid mode, in which the ratio is dynamically determined, for operation of the array in the hybrid mode; and

whether write-heat segregation is enabled for operation of the array in the hybrid mode.

11. The method of claim 10 , wherein the threshold level is defined as a capacity-usage level to transition between said the hybrid mode and multibit mode based on array-endurance.

12. The method of claim 10 , further comprising:

the memory controller monitoring workload-type during operation of the array; and

the memory controller dynamically defining the threshold level in dependence on the workload-type.

13. The method of claim 10 , further comprising:

the memory controller monitoring workload-type during operation of the array; and

the memory controller dynamically defining the threshold level in dependence on the workload-type.

14. A computer program product for controlling operation of an array of non-volatile memory cells comprising cells which are selectively configurable for single-bit and multibit storage, the computer program product comprising a computer readable storage medium having program instructions embodied therein, the program instructions being executable by a processing device of a memory controller to cause the memory controller to:

selectively configure the array for operation in a hybrid mode, in which the array comprises both cells configured for single-bit storage and cells configured for multibit storage, and a multibit mode in which all cells in the array are configured for multibit storage;

dynamically switch between the hybrid mode and multibit mode configurations of array corresponding to the array capacity-usage traversing a defined threshold level associated with enhancing an endurance of the array;

prior to operation of the array, defining the threshold level in dependence on a set of system parameters for the array, the parameters indicating information selected from the group consisting of:

raw cell endurance in the single-bit mode and multibit mode;

size of the array;

workload-type for the array;

one of a static-hybrid mode, in which a ratio of single-bit and multibit cells is static, and a dynamic-hybrid mode, in which the ratio is dynamically determined, for operation of the array in the hybrid mode; and

whether write-heat segregation is enabled for operation of the array in the hybrid mode.