Shadow memory system for storing variable backup blocks in consecutive time periods
US4959774A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 30, 1989 |
| Grant date | Sep 25, 1990 |
| Priority date | — |
| Expiry date | Jun 30, 2009 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F11/2015
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A highly reliable shadow memory system is able to survive multiple fast sequence power failures and includes a volatile main memory and a shadow memory subsystem which continually monitors write accesses to the main memory. The shadow memory subsystem includes a disk drive or shadow memory storing a copy of the data in main memory. As the main memory contents are altered, the shadow memory is continually updated to reflect the changes while main utility power is available. In the event of a main utility power failure, backup power is required to store main memory data in the shadow memory for only a few storage locations for which the updating of the shadow memory may lag main memory data changes. Consequently, only a small portion of available battery backup power is required to preserve all main memory data and the system can withstand multiple rapid succession power failures without loss of data.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.