Dynamically allocable RAM disk

Details Dynamically allocable RAM disk Dynamically allocable RAM disk

1998-02-26

2001-04-24

Nguyen, Than (Department: 2759)

Electrical computers and digital processing systems: memory

Storage accessing and control

Memory configuring

C711S004000, C711S104000, C711S105000, C711S170000, C711S172000, C711S173000, C711S217000, C707S793000, C707S793000

Reexamination Certificate

active

06223267

ABSTRACT:

FIELD OF THE INVENTION
This invention relates in general to memory storage devices and, more particularly, to simulating a physical storage device using random access memory.
BACKGROUND OF THE INVENTION
Static (conventional) RAM disks have been in use in computing devices for some time. A RAM disk is random access memory (RAM) that has been configured to simulate a disk drive. Files are accessed on a RAM disk just as they are on a physical disk. RAM disks are also known as RAM drives, virtual disks, and virtual drives.
Static RAM disks must be configured at system startup. After startup, the configuration of the static RAM disk cannot be changed. Once RAM has been allocated to a static RAM disk, it cannot be used by the system for processing. The memory allocated to the static RAM disk may only be used by the static RAM disk.
Additionally, static RAM disks require the user to configure the amount of memory that will be set aside for data storage. In many environments this makes the static RAM disk difficult to use, and requires frequent reconfiguration depending on changing patterns of system use.
SUMMARY OF THE INVENTION
According to principles of the present invention in a preferred embodiment, a system and method dynamically allocate memory to a RAM disk. Upon a file transfer to the RAM disk, a device driver determines an amount of memory required by the RAM disk, then requests the required amount of memory from a memory manager. As files are deleted from the RAM disk, the memory is released from the RAM disk by informing the memory manager of the addresses of the memory to be released.
According to further principles of the present invention in a preferred embodiment, data is written to the RAM disk in fixed increments called sectors. Sectors are grouped together to form clusters. The number of sectors in a cluster is dependent on the memory manager. A freelist is a bit map used to monitor the status of each sector of a cluster. When a sector becomes inactive, a corresponding bit in a sector freelist indicates the inactive status of the sector. When all of the sectors in a cluster are inactive, the cluster is released from the RAM disk.
Other objects, advantages, and capabilities of the present invention will become more apparent as the description proceeds.


REFERENCES:
patent: 4984149 (1991-01-01), Iwashita et al.
patent: 5359713 (1994-10-01), Moran et al.
patent: 5430858 (1995-07-01), Greeley et al.
patent: 5493574 (1996-02-01), McKinley
patent: 5548740 (1996-08-01), Kiyohara
patent: 5594903 (1997-01-01), Bunnell et al.
patent: 5606681 (1997-02-01), Smith et al.

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