US 5,634,109 A · Method and system for enhanced data management efficiency in memory subsystems utilizing redundant arrays of disk memory devices and a nonvolatile cache

Abstract

The present system may be utilized to minimize access performance penalties in memory subsystems which utilize redundant arrays of disk memory devices. Redundant arrays of disk memory devices provide levels of reliability which are not available with single storage devices; however, the redundancy carries with it an access performance degradation due to the requirement that such systems write data segments and parity elements to the array each time an application updates data within the system. A large nonvolatile cache is therefore provided in association with a redundant array of disk memory devices. Each time a data segment is written or read the data segment is staged from the array to the nonvolatile cache, if the data segment is not already within the cache. Additionally, if the operation is an update, a parity element associated with the data segment to be updated is also staged to the cache with the existing data segment content. An updated parity element is then calculated based upon the updated data, the existing data and the existing parity element. Data segments and associated parity elements are then maintained in the cache for future reading and updates until the number of updated data segments within the cache exceeds a predetermined value. Thereafter, selected data segments and associated parity elements are destaged from the cache to the array based upon a "Least Recently Utilized" (LRU) or "minimum seek" algorithm.

Claims17

Dependent claims

A method for enhanced data management in a memory storage subsystem which includes a nonvolatile cache and a redundant array of disk memory devices for storing a plurality of data segments and associated parity elements, said method comprising the steps of:

determining if a selected data segment and an associated parity element are present within said nonvolatile cache in response to an attempted update to said selected data segment;
staging said selected data segment and an associated parity element into said nonvolatile cache from said redundant array of disk memory devices in response to a determination that said selected data segment and an associated parity element are not present within said nonvolatile cache;
updating both said selected data segment and said associated parity element;
writing said updated selected data segment and said updated associated parity element into said nonvolatile cache;
and
destaging a data segment and an associated parity element from said nonvolatile cache into said redundant array of disk memory devices only in response to a number of updated data segments within said nonvolatile cache exceeding a predetermined number wherein access performance degradation associated with redundant arrays of disk memory devices is minimized.

3 more elements

A data processing system for permitting enhanced data management, said data processing system comprising:

a host processor;
a data storage subsystem, said data storage subsystem comprising:
a nonvolatile cache;
a redundant array of disk memory devices for storing a plurality of data segments and associated parity elements;
a control circuit for staging an image of a selected data segment and an associated parity element from said redundant array of disk memory devices into said nonvolatile cache in response to an attempted update thereto, for updating said selected data segment and said associated parity element, and writing said updated selected data segment and such updated associated parity element into said nonvolatile cache;
and
destaging means for destaging a data segment and an associated parity element from said non-volatile cache to said redundant array of disk memory devices only in response to a number of updated segments within said non-volatile cache exceeding a predetermined number, wherein access performance degradation associated with redundant arrays of disk storage devices is minimized.

4 more elements

A data storage subsystem for permitting the efficient management of data stored therein, said data storage subsystem comprising:

a nonvolatile cache;
a redundant array of disk memory devices for storing a plurality of data segments and associated parity elements;
a control circuit for staging an image of a selected data segment and an associated parity element from said redundant array of disk memory devices into said nonvolatile cache in response to an attempted update thereto, for updating said selected data segment and said associated parity element, and writing said updated selected data segment and said updated associated parity element into said nonvolatile cache;
and
destaging means for destaging a data segment and an associated parity element from said nonvolatile cache to said redundant array of disk memory devices only in response to a number of updated data segments within said nonvolatile cache exceeding a predetermined number wherein access performance degradation associated with redundant arrays of disk storage devices is minimized.

2 more elements

Dependencies are inferred from the claim text.

Method and system for enhanced data management efficiency in memory subsystems utilizing redundant arrays of disk memory devices and a nonvolatile cache

Life of this patent

Method and system for enhanced data management efficiency in memory subsystems utilizing redundant arrays of disk memory devices and a nonvolatile cache

Life of this patent

Abstract

Claims17