Minimum read rate throughput in a disk cache system
AssigneeEMC Corporation
InventorErez Ofer
Life of this patent
Estimating the term…
Abstract
A method and apparatus for maintaining a predetermined minimum read rate from a disk drive system, the disk drive system including a read/write cache memory, effect control over the write rate in response to data provided from the disk drive system. A host computer requests write cache utility factor information from the disk drive system. The response to the request provides the host computer with necessary information about the cache memory to enable it to control the write rate to not jeopardize the continuing flow of read data, for example, data for an audio or video decoding application. The host computer periodically samples the utilization of the cache memory and employs one of several methods for controlling the write rate to avoid adversely affecting the read data rate.
Claims23
A method for maintaining a predetermined minimum data read rate to a host computer from a disk drive system having an integral data read/write cache memory through which read and write data pass, wherein at different particular time instants, a same portion of the cache memory can be used for storing read and write data, comprising the steps of
- sending from the host computer a write cache utility factor inquiry,
- receiving, at the host system, write cache utility factor information,
- determining whether a write rate to the data read/write cache should be changed based on said utility factor information for the read/write cache memory, and
- modifying, if necessary in response to said determination step, the write rate to the data cache.
An apparatus for maintaining a predetermined minimum data read rate to a host system in a disk drive system having an integral data read/write cache memory through which read and write data pass, wherein, at different time instants, a same portion of the cache memory can contain read and write data, comprising
- the host system having a host system interface for requesting write cache utility factor information from the disk drive system,
- said disk drive system having
- a memory system interface for receiving said host factor request, and
- a controller connected to the memory system interface for processing said host factor request and for generating a response to said request based upon the read/write cache memory, and
- a write rate control at the host system for controlling the write rate to the data cache in response to said drive system controller response.
A disk drive system for enabling the maintenance of a minimum read rate in a disk drive system comprising
- an integral data read/write cache memory through which read and write data pass wherein at different time instants, a same portion of the cache memory can contain read and write data,
- a memory system interface for receiving from a host computer, a host utility factor request, and
- a controller, connected to the memory system interface for processing said host utility factor request and for generating a response to said request, said response including a value representative of at least two of:
- (i) the total available cache memory,
- (ii) a maximum write data cache memory permitted to enable the minimum read data rate to be maintained, and
- (iii) the current write cache memory being used for pending write data.
A disk drive system for maintaining a minimum data read rate comprising
- an integral data read/write cache memory through which read and write data pass, wherein, at different time instants, a same portion of the cache memory can contain read and write data,
- a disk drive controller,
- a memory system interface for receiving read and write requests from a host computer,
- the controller being connected to the memory system interface and to the read/write cache memory, for handling read and write requests to a disk drive storage,
- said disk drive controller being responsive to the utilization of the read/write cache memory for storing pending write data for preventing a response from the disk drive system to a write request from a host computer in order to maintain said minimum read rate from the disk drive system to a requesting host computer.
A method for maintaining a predetermined minimum data read rate from a disk drive system having in integrated data read/write cache memory through which read and write data pass, and wherein, at different time intervals, a same portion of the cache memory can be used for storing read and write data, comprising the steps of
- determining a write cache utility factor information for said read/write cache memory,
- determining whether fulfilling a further write request from a host computer will cause a read data flow to diminish below said minimum data read rate, and
- rejecting write requests from a requesting host if accepting said write request will cause said read data rate to drop below said minimum read data rate.
Dependencies are inferred from the claim text.