Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
2001-01-29
2004-12-14
Padmanabhan, Mano (Department: 2188)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C711S154000, C711S213000
Reexamination Certificate
active
06832288
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims priority of Japanese Patent Application No. 2000-019450, filed Jan. 28, 2000, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a read/write processing device and a read/write processing method for a disk recording medium. More particularly, the present invention relates to a read/write processing device for a disk medium that speeds up read/write processing by reordering commands and eliminating overlapping portions of write data.
2. Description of the Related Art
FIG. 2
is a block diagram of a conventional disk device
30
. As shown in
FIG. 2
, the conventional disk device
30
includes an internal write buffer
31
wherein read/write data is temporarily stored. More particularly, write commands are speeded up by storing data from a host computer in the write buffer
31
in response to a write command, and by returning a data write complete response to the host without waiting for a disk medium
32
to complete the data write. Commands pertaining to the write data accumulated in the write buffer
31
are held in a write command queue
33
, and write commands to write data to the disk medium
32
are executed by a command processor beginning with the oldest commands stored in the write command queue
33
. A continuous access decision unit
35
holds the last address
36
of the write data from an immediately preceding command and determines whether or not the write data of a write command currently executed accesses an address that is continuous with the last address
36
of the write data from the immediately preceding write command.
In recent years, improvements in performance of control processors in disk devices have made it possible to reorder the write commands in the write command queue
33
. More particularly, when there are multiple write commands in the write command queue
33
, the write commands can be reordered by calculating, for each command in the write command queue
33
, the head seek time plus the rotation wait time required to move to the start data from the final stored data position of the command currently under execution. The command corresponding to the transition that can be performed in the least amount of time is selected as the next write command. The reordering is performed by a reordering process
37
.
Conventional write command reordering processes are not efficient processes for a variety of reasons, as discussed below.
If there are write commands in the write command queue that have not yet been written to the recording medium and a new read command is entered, then the new read command must wait until all write commands in the write command queue have been processed before it is executed.
If write commands that are input continuously (in terms of time) are write commands that write data to continuous addresses, then the processing of the continuous write commands cannot continue if all of the other write commands in the queue have not been completed.
If a new write command is entered corresponding to write data that overlaps with that of a write command already in the write command queue, then no consideration is given to the continuity between the overlapping command in the queue and the new command that has been entered.
SUMMARY OF THE INVENTION
The present invention solves the above and other problems of the prior art by providing a read/write processing device and method for a recording medium that efficiently reorders write commands and eliminates overlapping data.
Embodiments of the present invention are achieved with a disk device, comprising a write buffer to store data for a write command received from a host. A command queue stores commands (read and write) for which an operation for accessing a disk medium has not been completed. A reordering processor returns a data write acknowledgment and selects from the write commands stored in the command queue a next write command to be executed, the next write command to be executed being a command having a starting data storage address on the disk medium that can be reached in the least amount of time from an address on the disk medium at which the last data of a command currently being executed is stored. A command processor executes the command selected by the reordering processor.
The disk device in accordance with embodiments of the present invention may further comprise a write command overlapping data processor checking for redundancies with the data of the write commands in the command queue in response to a read command being entered while a write command is being executed; and a read command starting processor returning the write command currently being executed to the command queue and executing the read command in response to the write command overlapping data processor confirming that there is no data redundancy.
In accordance with embodiments of the present invention, a newly input read command is set to the end of the command queue when the newly input read command includes read data overlapping with the write data among the write commands in the command queue or the write command being executed, and the reordering processor selects the write command having overlapping data and the command processor executes the read command last stored in the command queue when the write command having overlapping data is executed.
The disk device in accordance with embodiments of the present invention may further comprise a write command overlapping data processor checking for redundancies with the data of a write command in the command queue in response to a write command being entered while a write command is being executed, wherein the write command overlapping data processor overwrites an overlapping data part of an existing write command in the write buffer if a part of the accessed data for the new command includes redundancies with at least a part of accessed data for the existing write command in the command queue, and replaces a corresponding part of the existing write command in the write buffer with new data, and deletes the new command when accessed data of a new write command is completely included in the existing command.
The disk device in accordance with embodiments of the present invention may further comprise a continuous access decision unit storing in memory a starting address and an ending address of the accessed data from a previous command for write commands input continuously over time, and determining that an access is continuous if the starting address of the accessed data for a new write command is between the starting address and the ending address of the accessed data of the previous command; a write buffer storage device overwriting the data from the previous command in the write buffer and storing the write data from a host in a specified position in the write buffer; and a continuous access command storage unit storing a continuous series of write commands, wherein a continuous access operation is performed by moving a write data storage location for a new command to the starting position of the redundant data when, in the write commands that are input continuously over time, an earlier half of the actual command accessed data overlaps with a later half of the accessed data for the previous command.
The disk device in accordance with embodiments of the present invention may further comprise a write command overlapping data processor determining whether accessed data is redundant with data corresponding to a write command existing in the command queue in response to entry of a next write command, and if it is determined that a portion of the accessed data for the next write command is redundant with at least a portion of the accessed data of the write command in the command queue, deleting the redundant data from the existing write command in the write buffer; and a write buffer read device continually storing to the disk medium data that has been stored in different places in the write
Nishikawa Katsuhiko
Ohta Yoshiyuki
Fujitsu Limited
Namazi Mehdi
Padmanabhan Mano
Staas & Halsey , LLP
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