Electrical computers and digital processing systems: memory – Storage accessing and control – Specific memory composition
Reexamination Certificate
1998-08-26
2001-09-11
Kim, Matthew (Department: 2186)
Electrical computers and digital processing systems: memory
Storage accessing and control
Specific memory composition
C710S056000, C714S015000, C714S025000, C714S704000, C714S718000
Reexamination Certificate
active
06289416
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a disk drive device and a method for controlling the disk drive device for performing an improved write cache operation, and relates to a memory device and a method for controlling the memory device for performing the improved write cache operation.
2. Description of Related Art
In a hard disk drive device connected to a host processor through an interface, a write cache scheme has been used to save a processing time of the host processor. Describing the write cache scheme, when the hard-disk drive device is powered on, a main control circuit or MPU of the hard disk drive device enters into a POR (Power On Reset) status, and then enters into an initializing status in which many preparations for a read/write operation are made, e.g., a switching of a “write cache” status to an enable status. This status is called “write cache enable”.
An operation of the MPU in the write cache enable status is represented by a block
1
shown in
FIG. 1
, in which the MPU waits for a write command and data sent from the host processor, and when the write command and data are received, the MPU stores the data in a cache memory, as shown in a block
2
in FIG.
1
. The MPU then sends a write completion signal to the host processor through the interface, as shown in a block
3
. The operation proceeds to a block
4
, in which the MPU writes the data cached in the cache memory into the rotating data recording disk, such as a magnetic recording disk. The operation proceeds to an end block
5
to terminate the write cache operation. As described above, the MPU sends the write completion signal to the host processor before actually storing the data in the rotating data recording disk, so that the processing time of the host processor is saved.
Japanese patent application JP-A-8-77728 discloses a write cache scheme of a disk drive device connected to a host processor in which each time the disk drive device receives a write command from the host processor, a determination is made as to whether the write cache operation should be made. To this end, each time the write command is received, a cache monitor circuit monitors various parameters to determine as to whether the write cache mode should be turned ON or OFF. The parameters monitored by the cache monitor circuit are an error rate of an error correction circuit, an error rate at a verifying operation, a probability of occurrence of servo errors, etc. Japanese patent application JP-A-8-77728 is directed to control only the switching of the write cache mode ON or OFF, and does not discloses a control of a queue depth of the present invention.
A problem of the write cache scheme of the patent application JP-A-8-77728 is that the cache monitor circuit monitors the above various parameters to determine as to whether the write cache mode should be turned ON or OFF, each time the write command is sent from the host processor. It means that a command overhead is increased, and a write cache completion signal is sent to the host processor after a delay which is required to perform the operation of the cache monitor circuit, so that the processing time of the host processor is wasted.
It can be seen then that there is a need for a cache and method for caching that does not increase overhead or delays.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a disk drive device containing a cache memory having K queue entries (K is an integer) to operate in a write cache mode and a method for controlling the disk drive device in which the number of the queue entries to be used in the write cache mode can be gradually decreased from the number K to a number decreased by a predetermined number, and the number of the queue entries to be used in the write cache mode can be gradually increased from the decreased number towards the number K by a predetermined number, in response to values of parameters, such as an error rate and Non Repeatable Run Out or Repeatable Run Out of the rotating data recording disk at writing of data from the cache memory to a rotating data recording disk.
Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that a method for controlling a disk drive device containing a rotating data recording disk and a cache memory which includes K queue entries, wherein K is an integer, for storing data sent from a host processor, includes detecting that N queue entries in the cache memory store the data, wherein N is equal to or smaller than K, and N is an integer, successively writing the data stored in the N queue entries into the rotating data recording disk, detecting that an error rate at the writing of the data exceeds a predetermined level, and decreasing the K queue entries by a predetermined number X, wherein X is equal to or less than K−N, and X is an integer.
Another aspect of the present invention is that the detecting detects that an error rate at the writing of the data exceeds a predetermined level, and that Non Repeatable Run Out or Repeatable Run Out of the rotating data recording disk at the writing of the data exceeds a predetermined level.
Another aspect of the present invention is that a method for controlling a disk drive device containing a rotating data recording disk and a cache memory which includes K queue entries, wherein K is an integer, for storing data sent from a host processor includes detecting that at least one queue entry in the cache memory stores the data, writing the data stored in the queue entry into the rotating data recording disk, detecting an occurrence of error at the writing of the data, performing one of error recovery steps for the data, and rewriting the data into the rotating data recording disk, detecting that an error rate at the rewriting of the data into the rotating data recording disk exceeds a predetermined level, and decreasing the K queue entries by a predetermined number X, wherein X is equal to or less than K−N, N is the number of queue entries into which the data are stored, and N and X are integer.
Another aspect of the present invention is that the detecting detects that an error rate at the rewriting of the data exceeds a predetermined level, and that Non Repeatable Run Out or Repeatable Run Out of the rotating data recording disk at the rewriting of the data exceeds a predetermined level.
Yet another aspect of the present invention is that a method for controlling a disk drive device containing a rotating data recording disk and a cache memory which includes a plurality of queue entries for storing data sent from a host processor, to operate in a write cache mode includes detecting that at least one queue entry in the cache memory stores the data, writing the data stored in the queue entry into a target sector of the rotating data recording disk, detecting an occurrence of error at the writing of the data into the target sector, performing one of error recovery steps for the data and rewriting the data into the target sector, detecting that all error recovery steps are performed for the data, and that the rewriting of the data into the target sector fails, writing the data into an alternative sector of the rotating data recording disk, detecting that the writing of the data into the alternative sector succeeds, detecting that Non Repeatable Run Out or Repeatable Run Out of the rotating data recording disk exceeds a predetermined level, and informing the host processor of that a status of the disk drive device is switched to a status in which the disk drive device does not operate in the write cache mode.
Another aspect of the present invention is that a method for controlling a disk drive device containing a rotating data recording disk and a cache memory which includes a plurality of queue ent
Fukushima Yukio
Kakihara Toshio
Okutsu Kazushige
Ueda Tetsuo
Altera Law Group LLC
International Business Machines - Corporation
Kim Matthew
Vital Pierre H.
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