Power failure responsive apparatus and method having a shadow dram, a flash ROM, an auxiliary battery, and a controller

• US 5,799,200 A
• Filed: 09/28/1995
• Issued: 08/25/1998
• Est. Priority Date: 09/28/1995
• Status: Expired due to Term

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: EMC Corporation (Dell Technologies Inc.)
• Inventors: Tang, Edde Tin-Shek, Brant, William A., Nielson, Michael E.
• Primary Examiner(s): Sheikh, Ayaz R.
• Assistant Examiner(s): PANCHOLI, JIGAR K
• Application Number:
  US08/536,519
• Time in Patent Office: 1,062 Days
• Field of Search: 395/750, 395/427-497.04, 365/229
• US Class Current: 713/340
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: G06F 11/1441 Resetting or repowering

Abstract

Data in a system having dynamic random access memories (DRAM'"'"'s) is preserved despite loss of the primary source of electrical power to that system. A Flash RAM and a small auxiliary power source are employed by a controller independent of the system to transfer the DRAM contents to the Flash RAM immediately upon loss of primary system power. The data is also automatically returned to the DRAM after return of primary power with special data signals or sequences being utilized in a multiple controller environment so as to award the complete data recovery function to the first controller to demand attention.

Claims

1. Apparatus for preserving data that is stored in a volatile manner in a data processing system that is enabled by a primary electrical power source of a non-battery type that is subject to failure, said data processing system employing a first volatile dynamic random access memory for storing said data and a second volatile dynamic random access memory providing backup data storage for said data stored in said first volatile dynamic random access memory, comprising:

a non-volatile Flash ROM connectable to the data processing system;

a controller positioned together with said Flash ROM to be connectable to the data processing system together with connection of said Flash ROM to the data processing system including initializing means and data preservation means;

said initializing means responding to each initial application of power from the primary source to said data processing system for applying an erase signal to said Flash ROM for clearing said Flash ROM;

said data preservation means including loss of power detecting means for subsequently detecting loss of power from the primary power source;

said data preservation means including transferring means immediately responsive to said loss of power detecting means for transferring the data contained in said second dynamic random access memory into said Flash ROM;

an auxiliary battery power source positioned together with said Flash ROM and said controller; and

power applying means responsive to said loss of power detecting means for temporarily and immediately applying power from said auxiliary battery power source to said controller until such time as the data transfer from said second dynamic random access memory to said Flash ROM is completed.

2. Apparatus in accordance with claim 1 which includes power return sensing means responsive to return of power from the primary power source for returning data from said Flash ROM to said second dynamic random access memory.

3. Apparatus in accordance with claim 2 for use in conjunction with a data processing system having a plurality of controllers, each controller including a said power return sensing means, and each controller further including storing means for storing a signal indicating that said returning of data from said Flash ROM to said second dynamic random access memory was initiated by the associated said controller.

4. Apparatus in accordance with claim 3 wherein each said controller includes determining means for determining that a said signal was stored by said associated controller, said determining means operating to terminate said returning of data recovery from said Flash ROM to said second dynamic random access memory by an associated controller.

5. Apparatus for preserving data contained in a system enabled by a primary electrical power source of a type that is subject to periodic loss of power, said system employing a main volatile DRAM for exchanging data with a remote data processor and employing a volatile shadow DRAM for providing redundant backup for the main DRAM, comprising:

a non-volatile Flash ROM;

an auxiliary battery power source positioned to be carried together with said Flash ROM; and

a controller including initializing means and data preservation means positioned together with said Flash ROM and said auxiliary battery power source;

said initializing means responding to each initial application of power from the primary power source to the system for applying an erase signal to said Flash ROM for clearing said Flash ROM;

said data preservation means including detecting means for detecting loss of power from the primary power source, and temporary powering means powered by said auxiliary battery power source for responding to said detecting means for immediately transferring the data contained in the shadow DRAM into said Flash ROM, said temporary powering means remaining operative only until such time as the transfer of data from the shadow DRAM into said Flash ROM has been completed.

6. The method of preserving data that is contained in a data processing system that is enabled by a primary electrical power source of a type that is subject to failure, which system employs at least one volatile DRAM unit mounted at a mounting base, comprising the steps of:

providing a non-volatile Flash ROM at the mounting base;

providing an auxiliary battery power supply at the mounting base;

clearing the contents of said Flash ROM;

sensing that said primary power source is no longer supplying power to the system;

immediately transferring the data contents present in said DRAM into said Flash ROM upon sensing that said primary power is no longer supplying power to the system;

recognizing that said primary power source is again supplying power to the system;

returning the data from said Flash ROM to said DRAM; and

utilizing an auxiliary battery power source for transferring the contents of said DRAM into said Flash ROM only during a time interval of said transferring step.

7. The method in accordance with claim 6 which further includes the steps of;

storing a signal indicating that said data returning step was initiated,

determining that said signal has been previously stored, and

preventing a subsequent execution of said data returning step when it is determined that said signal has been previously stored.

8. Apparatus for preserving data that is stored in a volatile manner within a data processing system that is enabled by a primary electrical power source of a non-battery type that is subject to a loss of power, the data processing system employing a first volatile dynamic random access memory for storing data, the data processing system further employing a second volatile dynamic random access memory that provides backup data storage for the first volatile dynamic random access memory, and the second volatile dynamic random access memory being physically removable from the data processing system, said apparatus comprising:

a mounting base physically replacing the second volatile dynamic random access memory;

a third volatile dynamic random access memory mounted on said mounting base to be carried therewith;

said third volatile dynamic random access memory providing backup data storage for the first volatile dynamic random access memory;

a non-volatile Flash ROM mounted on said mounting base together with said third volatile dynamic random access memory to be carried with said mounting base;

a controller mounted on said mounting base together with said third volatile dynamic random access memory to be carried by said mounting base;

an auxiliary battery power source mounted on said mounting base together with said third volatile dynamic random access memory and said non-volatile, said auxiliary battery power source connected to selectively provide battery power to said controller, said controller including initializing means and data preservation means;

said controller initializing means responding to each initial application of power from the primary source to the data processing system for applying an erase signal to said non-volatile Flash ROM for clearing said non-volatile Flash ROM;

said controller data preservation means including loss of power detecting means for subsequently detecting loss of power from the primary power source;

said controller data preservation means including transferring means immediately responsive to said loss of power detecting means for transferring data contained in said third volatile dynamic random access memory into said non-volatile Flash ROM;

said controller data preservation means being responsive to said controller loss of power detecting means for temporarily and immediately applying power from said auxiliary battery power source to said controller until such time as data transfer from said third volatile dynamic random access memory to said non-volatile Flash ROM has been completed.

9. Apparatus for preserving data contained in a system that is enabled by a primary electrical power source of a type that is subject to periodic power loss, the system employing a first volatile-DRAM for exchanging data with a remote data processor, and the system employing a physically removable second volatile-DRAM for providing redundant data backup for the first volatile-DRAM, comprising:

a mounting base physically replacing the second volatile-DRAM;

a third volatile-DRAM mounted on said mounting base to be carried therewith, said third volatile-DRAM replacing the second volatile-DRAM as a redundant data backup for the first volatile-DRAM;

a non-volatile Flash ROM mounted on said mounting base together with said third volatile DRAM to be carried by said mounting base;

a controller mounted on said mounting base together with said third volatile DRAM and said controller;

an auxiliary battery power source mounted on said mounting base together with said third volatile DRAM, said non-volatile Flash ROM, and said controller;

initializing means within said controller;

data preservation means within said controller;

first means included said initializing means responding to each initial application of power from the primary power source to the system for applying an erase signal to said non-volatile Flash ROM for clearing said non-volatile Flash ROM;

second means including said data preservation means for detecting loss of power from the primary power source, and operating in response to a said detected loss of power from the primary power source to utilize said auxiliary battery power source to immediately transfer data contained in said third volatile-DRAM into said non-volatile Flash ROM;

said second means remaining operative only until such time as said transfer of data from said third volatile-DRAM into said non-volatile Flash ROM has been completed.

10. Modular memory apparatus for a data processing system susceptible to interruption of system power provided by a primary electrical power source, said modular memory apparatus comprising:

a module connectable to the data processing system;

a volatile memory element at least carried by said module, said volatile memory element for storing data accessible during operation of the data processing system;

a non-volatile memory element at least carried by said module together with said volatile memory element, said non-volatile memory element for storing at least some of the data stored in said volatile memory element;

an auxiliary battery power source carried by said module together with said volatile memory element and said non-volatile memory element; and

a controller at least carried by said module together with said volatile memory element, said non-volatile memory element, and said auxiliary battery power source, said module, together with said volatile memory element, said non-volatile memory element, said auxiliary battery power source connectable as a single unit to said data processing system, said controller for detecting the interruption of the system power and, responsive thereto, to effectuate powering of said controller by said auxiliary battery power source, and for effectuating transfer of the data stored in said volatile memory element to said non-volatile memory element.