Electrical computers and digital processing systems: support – Computer power control
Reexamination Certificate
1999-02-04
2001-12-18
Dharia, Rupal (Department: 2181)
Electrical computers and digital processing systems: support
Computer power control
C713S320000, C713S323000, C713S324000, C711S111000, C710S052000, C360S060000, C360S067000, C360S069000, C360S075000
Reexamination Certificate
active
06332196
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a disk storage apparatus suitable for reduction in power consumption in a disk access operation. The invention also relates to a power supply control method suitable for reduction in power consumption in a disk access operation.
In general, a function called “preread cache” is provided in a disk storage apparatus, such as a hard-disk drive (HDD), which is connected in use to a host system (hereinafter referred to simply “host”) such as a computer system via a host interface.
In the preread cache function, after sectors requested by a read command from the host are read out from a disk (disk medium) and transmitted, data of sectors having sector numbers following the sector number of the last one of the read-out sectors is preread onto a buffer memory in the order of sector numbers. If a sector requested by the next read command from the host coincides with the preread sector, the associated data on the buffer memory is immediately transferred to the host without access to the disk. With this function, the performance of the interface between the disk storage apparatus and the host can be enhanced.
The details of the preread cache function will now be described with reference to FIG.
1
and
FIGS. 2A
to
2
D.
The data of n-sectors, i.e. sector A through sector B, on a disk
180
shown in
FIG. 1
which have been requested by a read command R
1
from the host is read from the disk
180
onto a read-data buffer region (cache region) defined in a buffer memory
181
under control of an HDC (disk controller), and the data is transferred in parallel to the host (see FIG.
2
A). If the transfer of the data requested by the read command R
1
is completed, preread is effected.
In general, however, the buffer memory
181
has a less capacity than the disk
180
. For example, at the time when sectors from sector B+1((n+1)th sector), which follows sector B, to sector C ((n+m)th sector) have been preread, the buffer memory
181
(or the read-data buffer region thereof) becomes full (see
FIG. 2B
) and no space remains in the buffer memory
181
for storing the read data. The HDC which controls the buffer memory
181
detects this state and stops the preread.
If the next read command R
2
from the host has made a cache hit (i.e. coincidence between the sector read in the buffer memory
181
and the sector requested by the host) and the hit sector data has been transferred to the host and as a result space has been caused in the buffer memory
181
(see FIG.
2
C), preread is resumed from sector C+1 (=D) following the last sector (last read-out sector) C preread before the previous preread was stopped (see FIG.
2
D).
In the prior art, in order to reduce the power consumption of the HDD in a time period between the temporary stop of preread and the resumption of preread, there is known a method in which power supply to the circuit elements relating to R/W (read/write), that is, R/W circuits relating to read/write channels, disk access of the HDC, etc., is stopped.
An operation in the above prior art, which follows the completion of preread and is accompanied with the above-mentioned power supply control, will now be described with reference to
FIGS. 3A and 3B
.
In the prior-art technique, the CPU needs to check, at regular intervals, whether space has been caused in the buffer memory. In this case, in order to resume the preread in a shortest time after space has been caused in the buffer memory, the CPU needs to check the buffer memory at a timing at which the sector D, which follows the last sector C read by the preread cache function, has reached a position where read by the magnetic head is permitted at every rotation of the disk
180
.
However, if the generation of check timing of the buffer memory is performed only with a timer (CPU timer) of the CPU, the check timing may gradually be shifted due to a timer error from the timing at which the subsequently read sector D reaches the position of the magnetic head. In such a case, an excess time may be needed to actually start read-out after the presence of space is confirmed.
In the prior art, with use of the CPU timer, a timing (i.e. timing at sector X in
FIG. 3A
) is provided several servos (one servo normally including 2 to 5 sectors) before the subsequently read-out sector D, that is, the next target sector D, arrives at the position of the magnetic head. At this timing, a check is started as to whether space is present in the buffer memory (step P
1
) and power supply to the P/W circuit is resumed (step S
2
).
Then, it is checked whether space exists in the buffer memory (step P
3
).
If there is no space in the buffer memory, the position of the last sector C read out by the preread cache is confirmed, and the CPU timer is reactivated to generate timing of the sector X. After the power to the R/W circuit turned off (step P
4
), the control returns to step P
1
. On the other hand, if there is space in the buffer memory, the read-out of sectors beginning with the target sector D is started (step P
5
).
This method is similarly applied to the write operation. After a write command is completed or when transfer of data from the host has been temporarily stopped, all data transmitted from the host and stored in the buffer memory are written in the disk. If the buffer memory becomes empty in consequence, the CPU stops power supply to the R/W circuit.
In anticipation of write to the next sector, it is checked whether the buffer has become not empty, at every rotation of the disk at a timing generated by the CPU timer. In addition, in order to prevent this timing from shifting from the position of the sector on which data is to be written next, power supply to the R/W circuit is resumed/stopped at every rotation of the disk.
In the above-described prior art, in order to prevent power from being consumed in vain by the R/W circuit while the read/write operation is not actually performed, power supply to the R/W circuit is temporarily stopped and is reapplied to the R/W circuit before a predetermined time read/write operation is resumed in the state in which the buffer memory is full in the read operation and empty in the write operation, and it is checked whether the read/write operation can be resumed.
More specifically, in the above prior art, even after the buffer memory has become full due to the preread cache of the read operation, it is necessary to check the empty state of the data buffer at regular intervals. For this check, power is supplied to the R/W circuit at regular intervals. As a result, power is supplied to the R/W circuit at every rotation of the disk until the next read/write command is issued from the host. According to this method, compared to a method in which power is constantly supplied, the power consumption can be reduced. However, power is consumed to some degree since it is supplied to the R/W circuit at regular intervals until the next command is issued.
In the write operation, too, if the buffer memory has become empty, power is supplied to the R/W circuit at regular intervals, and power is consumed to some degree.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made in consideration with the above situation, and its object is to provide a disk storage apparatus which detects that a buffer memory has a space by a disc controller for controlling the buffer memory and to supply power to a R/W circuit in accordance with the detection result when read operation is executed thereby reducing power consumption in the R/W circuit until next read command is issued from a host. The present invention also provide a power supply control method therefore.
Another object of the present invention is to provide a disk storage apparatus which detects that a buffer memory becomes not empty by a disc controller itself for controlling the buffer memory and to supply power to a R/W circuit in accordance with the detection result when write operation is executed thereby reducing power consumption in the R/W circuit until next read
Ichikawa Yasuhiko
Ishii Shuichi
Kawasaki Makoto
Dharia Rupal
Kabushiki Kaisha Toshiba
Pillsbury & Winthrop LLP
LandOfFree
Disk storage apparatus and power supply control method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Disk storage apparatus and power supply control method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disk storage apparatus and power supply control method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2581896