U.S. patent application number 11/327902 was filed with the patent office on 2006-06-01 for system and method to enable efficient communication with a dynamic information storage and retrieval system, or the like.
Invention is credited to Yasutomo Matsuba, Satoru Yamauchi.
Application Number | 20060117137 11/327902 |
Document ID | / |
Family ID | 33298121 |
Filed Date | 2006-06-01 |
United States Patent
Application |
20060117137 |
Kind Code |
A1 |
Matsuba; Yasutomo ; et
al. |
June 1, 2006 |
System and method to enable efficient communication with a dynamic
information storage and retrieval system, or the like
Abstract
An information storage and retrieval system (40) and method for
operating same has a host device (42) and an information storage
device (41), which includes mass data storage means (54), such as a
DVD, a DVD RAM, CD-ROM, alone, or in combination. The information
storage device (41) includes a cache memory (48) for holding data
as it is being written to the mass data storage means (54). The
host device (42) is connected to the cache memory (48) to control a
size of the cache memory that can be utilized to hold the data to
be written to the mass data storage means (54), to control, for
instance, the flush, seek, busy, and/or overhead times of the
information storage device (41).
Inventors: |
Matsuba; Yasutomo; (Ibaraki,
JP) ; Yamauchi; Satoru; (Ibaraki, JP) |
Correspondence
Address: |
TEXAS INSTRUMENTS INCORPORATED
P O BOX 655474, M/S 3999
DALLAS
TX
75265
US
|
Family ID: |
33298121 |
Appl. No.: |
11/327902 |
Filed: |
January 9, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10249646 |
Apr 28, 2003 |
7017006 |
|
|
11327902 |
Jan 9, 2006 |
|
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Current U.S.
Class: |
711/113 ;
711/E12.019 |
Current CPC
Class: |
G06F 2212/313 20130101;
G06F 2212/601 20130101; G06F 2212/211 20130101; G06F 12/0873
20130101 |
Class at
Publication: |
711/113 |
International
Class: |
G06F 13/00 20060101
G06F013/00 |
Claims
1. An information storage and retrieval system, comprising: an
information storage device; said information storage device
including a cache memory for holding data as it is being written to
said information storage device; and a host device associated with
said information storage system, said host device being connected
to said cache memory to control a size of said cache memory that
can be utilized to hold said data.
2. The information storage and retrieval system of claim 1 wherein
said information storage device comprises a DVD drive.
3. The information storage and retrieval system of claim 1 wherein
said information storage device comprises a DVD RAM.
4. The information storage and retrieval system of claim 1 wherein
said information storage device comprises a CD-ROM drive.
5. The information storage and retrieval system of claim 1 wherein
said information storage device comprises a both a DVD drive and a
CD-ROM drive.
6. An information storage and retrieval system, comprising: an
information storage device; said information storage device
including a cache memory for holding data as it is being written to
said information storage device; and a host device connected to
said information storage system to control a flush time
thereof.
7. The information storage and retrieval system of claim 6 wherein
said information storage device comprises a DVD drive.
8. The information storage and retrieval system of claim 6 wherein
said information storage device comprises a DVD RAM.
9. The information storage and retrieval system of claim 6 wherein
said information storage device comprises a CD-ROM drive.
10. The information storage and retrieval system of claim 6 wherein
said information storage device comprises a both a DVD drive and a
CD-ROM drive.
11. An information storage and retrieval system, comprising: an
information storage device; said information storage device
including a cache memory for holding data as it is being written to
said information storage device; and a host device connected to
said information storage system to control an overhead time
thereof.
12. The information storage and retrieval system of claim 11
wherein said information storage device comprises a DVD drive.
13. The information storage and retrieval system of claim 11
wherein said information storage device comprises a DVD RAM.
14. The information storage and retrieval system of claim 11
wherein said information storage device comprises a CD-ROM
drive.
15. The information storage and retrieval system of claim 11
wherein said information storage device comprises a both a DVD
drive and a CD-ROM drive.
16. An information storage and retrieval system, comprising: an
information storage device; said information storage device
including a cache memory for holding data as it is being written to
said information storage device; and a host device connected to
said information storage system to control a busy time thereof.
17. The information storage and retrieval system of claim 16
wherein said information storage device comprises a DVD drive.
18. The information storage and retrieval system of claim 16
wherein said information storage device comprises a DVD RAM.
19. The information storage and retrieval system of claim 16
wherein said information storage device comprises a CD-ROM
drive.
20. The information storage and retrieval system of claim 16
wherein said information storage device comprises a both a DVD
drive and a CD-ROM drive.
21-31. (canceled)
32. A method for determining a cache size used in an information
storage and retrieval system of the type having a host device
interfaced to at least one mass data storage device by a bus,
comprising: determining an overhead time required by said host
device; determining said cache size by multiplying a writing speed
of said mass data storage device by the difference between an
overhead time and a seek time.
33. A method for determining a cache size used in an information
storage and retrieval system of the type having a host device
interfaced to at least one mass data storage device by a bus,
comprising: determining a busy time required by said host device;
determining said cache size by multiplying said busy time by a sum
of a writing speed of said mass data storage device and a speed of
said bus.
34-40. (canceled)
Description
BACKGROUND OF INVENTION
[0001] 1. Field of Invention
[0002] This invention relates to improvements in methods and
apparatuses for dynamic information storage and retrieval, and more
particularly to improvements in dynamic information storage systems
of the type having associated mass data storage devices, such as
DVDs, CDROMs, or like devices, and still more particularly to
improvements in methods for managing, allocating, or controlling a
cache memory in such dynamic information storage and retrieval
systems depending upon the specifications of mass data storage
devices associated therewith, and systems for using same.
[0003] 2. Relevant Background
[0004] As used herein, the term "dynamic information storage
system" includes digital systems that have one or more mass data
storage devices to which digital data may be selectively written
and read back. Some dynamic information storage systems, for
example, may include one or more digital video disk (DVD) devices
alone, or in combination with one or more compact disk read-only
memory (CD-ROM) devices. The data storage devices may be interfaced
to a system bus, a typical bus that is currently popular in use
being, for example, the ATAPI bus, although other buses can be
used.
[0005] Mass data storage devices include tape drives, RAM drives,
as well as hard disk drives that have one or more spinning magnetic
disks or platters onto which data is recorded for storage and
subsequent retrieval. Hard disk drives may be used in many
applications, including personal computers, set top boxes, video
and television applications, audio applications, or some mix
thereof. Applications for hard disk drives are still being
developed, and are expected to further increase in the future. Mass
data storage devices may also include optical disks in which the
optical properties of a spinning disk are locally varied to provide
a reflectivity gradient that can be written and detected by laser
transducer heads, or the like. Optical disks may be used, for
example, to contain data, video signals, music, or other
information.
[0006] In dynamic information storage systems, typically a host
device or system may be required to interface to the system, yet,
as mentioned, a single dynamic information storage system may
include either a DVD type, CD-ROM type, or both types of mass data
storage devices. Such devices are now being provided, for example,
in systems in which both audio and video data can be written to the
respective mass data storage devices associated with the system.
This can create a problem in that relatively long times are
required in order to fully record data to DVD systems, especially
in comparison to the relatively shorter time that is required to
write audio data to a CD-ROM mass data storage device. Because the
wait times of different types of mass data storage devices may
differ, the efficiency of the system may not be optimal for a
particular host.
[0007] Typically, in the construction of dynamic information
storage systems, the communication between a host and the
associated mass data drive(s) should be taken into consideration.
If, for example, a DVD drive is included, the system would
typically have a long busy time during communication, because DVD
drives have a slow response. This factor restricts the freedom of
the structure of the host. For example, in order to accommodate the
long busy time, the host needs a large memory as a communication
buffer. This makes the system larger and more complex than
otherwise would be required if the busy time were not so long.
[0008] In the design of DVD drives, and particularly in the
combination of a DVD drive with a host device, typically trade-offs
need to be made. For example, some DVD drives have different busy
and overhead times, but, nevertheless have the same DVD writing
speed.
[0009] In some applications, a small overhead time may be better in
a system in which the data transfer frequently changes direction,
for example, in a read/write operation. On the other hand, in other
installations, a small busy time may be better in a system in which
the host performs a number of write operations to the DVD device in
frequent succession. As will be seen in the detailed description
below, the overhead and busy times depend upon the size of the
cache.
[0010] In the past, however, the size of the cache could not be
changed in the design the system. Therefore, depending upon the
particular application, it has been important to select the proper
drive to meet the particular needs of the application. For example,
a drive having a small overhead time may be selected in those
applications which have frequent changes in the data direction.
Moreover, once the drive is selected to meet the particular
application needs, the host device needs to be selected to adapt to
the particular drive that is selected.
[0011] This difficulty is further compounded when a system is
designed in which several applications may be combined into a
single device, and, in particular, in cases in which some
applications require a short overhead and other applications
require a short busy time. In the past, the design of a host in
such cases was a trade-off considering the unchangeable
characteristics of the drives.
[0012] What is needed, therefore, is a method and system that
provides efficient communication between a host and its associated
data storage systems, regardless of the construction of the dynamic
information storage systems with regard to the types of mass data
storage devices associated therewith.
SUMMARY OF INVENTION
[0013] One advantage of the present invention is that it provides a
method to reduce the effects of long busy times during data write
actions in some data storage systems. Long busy times are prevalent
in many data storage systems, or the like, particularly when the
data storage system includes different types of mass data storage
devices that have different write speeds.
[0014] It is another advantage of the invention is that the host of
a dynamic information storage and retrieval system is enabled to
control the flush, seek, busy, and/or overhead times in an
information storage and retrieval system.
[0015] According to a broad aspect of the invention, an information
storage and retrieval system is presented that has an information
storage device and a host device. The information storage device
includes a cache memory for holding data as it is being written to
the information storage device. The host device is connected to the
cache memory to control a size of the cache memory that can be
utilized to hold the data. The information storage device may
include, for example, a DVD, a DVD RAM, CD-ROM, alone or in
combination.
[0016] According to another broad aspect of the invention, an
information storage and retrieval system is presented that has an
information storage device and a host device. The information
storage device includes a cache memory for holding data as it is
being written to the information storage device. The host device is
connected to the information storage system to control a flush time
thereof.
[0017] According to yet another broad aspect of the invention, an
information storage and retrieval system is presented that has an
information storage device and a host device. The information
storage device includes a cache memory for holding data as it is
being written to the information storage device. The host device is
connected to the information storage system to control an overhead
time thereof.
[0018] According to yet another broad aspect of the invention, an
information storage and retrieval system is presented that has an
information storage device and a host device. The information
storage device includes a cache memory for holding data as it is
being written to the information storage device. The host device is
connected to the information storage system to control a busy time
thereof.
[0019] According to still another broad aspect of the invention, a
data storage system is presented. The data storage system includes
a host device for delivering data to be written to the data storage
system. The data storage system also includes a system bus, at
least one mass data storage device connected to the system bus, a
cache memory, and a controller to control the cache memory. The
controller is connected to allocate an amount of the cache memory
to receive the data to be written to the data storage system. The
host device is configured to control the controller to allocate an
amount of the cache memory to receive the data to be written to the
data storage system according to a specification of the at least
one mass data storage device connected to the system bus.
[0020] The system bus may be, for example, an ATAPI bus. The host
device may be connected to effectively control an overhead time, a
busy time, a seek time, or a flush time by controlling a write and
read allocation of the cache memory.
[0021] According to still yet another broad aspect of the
invention, a data storage system is presented of the type having at
least one mass data storage device associated therewith. The data
storage system includes a data bus and a cache memory connected to
the data bus to receive data from a data source to be written to
the data storage system. Means are also provided for allocating the
cache memory depending upon a specification of the at least one
mass data storage device.
[0022] According to yet still another broad aspect of the
invention, a method is presented for determining a cache size used
in an information storage and retrieval system of the type having a
host device interfaced to at least one mass data storage device by
a bus. The method includes determining an overhead time required by
the host device and determining the cache size by multiplying a
writing speed of the mass data storage device by the difference
between an overhead time and a seek time.
[0023] According to still another broad aspect of the invention, a
method is presented for determining a cache size used in an
information storage and retrieval system of the type having a host
device interfaced to at least one mass data storage device by a
bus. The method includes determining a busy time required by the
host device and determining the cache size by multiplying the busy
time by a sum of a writing speed of the mass data storage device
and a speed of the bus.
[0024] According to another broad aspect of the invention, a method
is presented for operating a data storage system that includes a
memory cache. The method includes determining a specification of at
least one mass data storage device within the data storage system
and allocating an amount of the cache memory for writing data to
the data storage system, depending upon the specification that is
determined.
[0025] According to another broad aspect of the invention, a mass
data storage device is presented. The mass data storage device
includes a data recording media and a controller to control the
recording of data to the data recording media. A cache memory is
provided to data to be written to the data recording media,
controlled by the controller. The cache memory is configurable,
having a selectable write size as determined by the controller. The
controller may be configured to accept commands from an external
host device to establish the write size of the cache memory.
BRIEF DESCRIPTION OF DRAWINGS
[0026] The invention is illustrated in the accompanying
drawing.
[0027] FIG. 1 is a block diagram showing a recording system that
can be used with a DVD-recorder, a hard disk-recorder, or the like,
in which the method or system of the present invention may be
embodied.
[0028] FIG. 2 is a diagram showing a writing and reading sequence
of a memory system that may be used in conjunction with the video
recording system of FIG. 1.
[0029] FIG. 3 is a block diagram of the structure of a typical DVD
drive, in which the method or system of the present invention may
be embodied.
[0030] FIG. 4 is a block diagram of a system that may be used to
access both a DVD drive and a hard disk drive, in which the method
or system of the present invention may be embodied.
[0031] FIG. 5 is a graph of the data size of the writing command
vs. busy time of a typical hard disk drive, in which the method or
system of the present invention may be embodied.
[0032] In the various figures of the drawing, like reference
numerals are used to denote like or similar parts.
DETAILED DESCRIPTION
[0033] In many mass data storage devices, long busy times are
prevalent. The present invention presents a method and apparatus or
circuit to control such long busy times. This is accomplished by
providing a new communication method between a mass data storage
device and its host, the combined system being referred to herein
as a dynamic information storage and retrieval system.
[0034] Typically, in the construction of dynamic information
storage and retrieval systems that include such functions as DVD
recorders, hard disk recorders, or some combination thereof, a mass
data storage device or drive is generally necessary. To design such
system, the communication between the host and the drive should be
taken into consideration. However, because a DVD drive is a slow
response device, which has a long busy time during communication,
the freedom of the structure of the host is restricted. This is
primarily due to the fact that in order to accommodate the long
busy time, the host needs a large memory as a communication buffer.
This makes the system larger and more complex than otherwise would
be required if the busy time were not so long.
[0035] However, according to a preferred embodiment of the present
invention, the host is enabled to vary the size of the cache memory
of the data storage system with which it is associated, thereby
effectively controlling the overhead and busy times, as described
in detail below. This eliminates the need for a large memory or
buffer, as heretofore required, simplifying the host design.
[0036] A block diagram of a dynamic information storage system 10
that can be used with a DVD-recorder, a hard disk-recorder, or the
like, is shown in FIG. 1, in which the method or system of the
present invention may be embodied. The dynamic information storage
system 10 has a host data system 12 that provides data
communication with one or more mass data storage devices through a
system bus, an ATAPI bus 14 being shown, for example. Although an
ATAPI bus is shown, it should be understood that other bus types
may be used, such as, for example, buses of various ATAPI versions,
SCSI buses, and so on. The host data system 12 is of the type that
has at least a CPU and program that is executed thereby.
[0037] As shown, the dynamic information storage system 10 can
include a DVD drive 16, which has a capability of writing to and
reading from a DVD disk 18. The dynamic information storage system
also may have a hard disk drive 20, which also has a capability of
being written to and read from. As mentioned above, in the past,
the host 12 was generally designed to accommodate the type of mass
data storage device, which might be interfaced to the ATAPI bus,
which would represent the "worst-case" wait-time that might be
anticipated. However, in accordance with a preferred embodiment of
the invention, the host 12 can dynamically configure a cache write
memory (not shown) that may be associated with the dynamic
information storage system 10 to efficiently effect a write
operation to whatever type of mass data storage device that may be
associated.
[0038] FIG. 2, to which reference is now additionally made, shows a
stylized graph as a function of time showing an example of the
various functions of a typical dynamic information storage system
of the type shown in FIG. 1, including a typical writing and
reading sequence. A typical dynamic information storage system may
be, for example, a DVD drive, or the like.
[0039] As shown, an access period 22 includes a write period 24, a
read period 26, and an overhead time 28 separating the write period
24 and the read period 26. The access period 22 may be repeated a
number of times, as shown. The write period 24 may include a host
access that recurs, for example, 100 times, to perform processes
referred to herein as "write cycles". Similarly, the read period 26
includes a read process executed by the host, for instance, 100
times, to perform processes referred to herein as "read cycles". It
should be noted that although the write and read cycles have been
illustrated as repeating 100 times, various systems may have other
read and write repeating patterns and frequencies, depending upon
their particular applications.
[0040] An expanded view of a portion of the write period 24 that
includes two host write cycles is shown beneath the access period
22. Each of the write cycles includes a data transfer time 30,
followed by a busy time 32. The sum of the write time 30 and busy
time 32 is defined as the "T-period" 34.
[0041] With reference again to the upper portion of the graph, the
overhead period 28 includes a time referred to as a "flush" time
27, and a time referred to as a "seek" time 29. The flush time 27
is the time during which data failed to be written to the dynamic
information storage system during the write period 24. The seek
time is the time required for the heads of the dynamic information
storage system to acquire the position at which data is to be read
from the dynamic information storage system in a read cycle of a
subsequent read period 26.
[0042] The overhead time is shown between the writing and reading
operations. It is caused by flush and seek processes. The busy time
is shown at each writing process, as noted particularly in the
bottom of FIG. 2. In order to understand the reason why the flush,
seek, and busy processes occur, we need to understand the data flow
of a DVD drive.
[0043] Thus, another example of a structure of a typical
information storage and retrieval system 40 is shown in the context
of a DVD drive 41 in FIG. 3, to which reference is now additionally
made. The information storage and retrieval system 40 may be used
to illustrate the importance of the flush, seek, and busy
processes, noted above. A host machine 42, which is connected to a
track buffer 46, is interfaced to the DVD drive 40 via an ATAPI bus
44. The host machine 42 may be configured in a manner similar to
the host machine 12 described above in conjunction with FIG. 1,
including at least a CPU and program means that is executed
thereby. Within the DVD drive 40, the ATAPI bus interfaces with a
cache memory 48 for write and read processes 50 and 52.
[0044] The data to be written to the DVD disk 54 is first loaded
into the cache memory 48, and, under the control of the controller
56, is transferred to appropriate writing heads (not shown) to be
written to the disk 54. Similarly, data to be read from the disk
54, is detected by the read heads (also not shown), and, under the
control of controller 56, is delivered to the cache memory 48. The
read the data is then transferred via the ATAPI bus to the host 42
for use.
[0045] Thus, in operation, the data flow of a writing process of
the DVD drive 40 is as follows. The host 42 sends a write command
to the DVD drive 40. The data is transferred from the host 42 to
the DVD drive 40. This is referred to herein as the "data transfer
process". The data transfer process is illustrated in FIG. 2 above,
and denoted by the reference numeral 30. During the data transfer
process 30, the data is transferred into the cache memory 48. After
the data transfer is finished, all or a portion of the data in the
cache is recorded to the DVD disk 54.
[0046] During this time, the host may be unable to access the drive
40. This is referred to herein as a "busy process". As indicated
above, this data writing cycle may be repeated a number of times,
for example, 100 times. After the required number of cycles, the
host 42 completes the write command. Within the DVD drive 40, after
the completion of the writing process, some of the data to be
written may remain within the cache 48. As noted above, during the
overhead period 28, any such remaining data is then written to the
disk 54 in a process referred to as a "flush process". The time of
the flush process is herein referred to as the "flush time", and
depends on how much data exists in the cache when the write command
is finished. The flush time can be determined from the size of the
cache needed during the writing operation.
[0047] The seek process includes the time used to seek the starting
address of the data to be read. The seek time is also known, being
specific to any particular drive. Thus, the overhead time, being
the sum of the flush time and seek time, can be determined from the
specification of the cache size and the seek time for any
particular drive.
[0048] As indicated, the busy time depends on the sum of the data
transfer time and the "T-period". Both the data transfer time and
the "T-period" can be determined from the amount of data to be
transferred during the writing command.
[0049] In accordance with the present invention, the host device 42
can effectively set the size of the cache memory 48 by sending an
appropriate command to the controller 56 of the DVD drive 40. Thus,
the construction of the host device 42 as well as the associated
dynamic information storage and retrieval can be accomplished in a
way that the allocated size of the buffer memory 48 can be varied
as needed, depending upon the configuration of the particular
drive. This enables the host device 42 to operate in different
modes that can be selected by a user. For example, one mode may be
a "start/stop DVD recording" mode. Another mode may be a "start HDD
accessing mode, and so on.
EXAMPLE 1
[0050] As an example of specifying a DVD-RW drive, the following
parameters may be assumed:
[0051] cache size in writing operation=1.5 MB
[0052] disc writing speed=1.38 MB/sec.
[0053] seek time=200 msec
[0054] ATAPI bus speed=16.6 MB/sec. (PIO transfer mode 4)
[0055] data size of writing command=128 KB
[0056] from the above specification, the overhead time and the busy
time can be calculated as follows:
[0057] Flush time=(cache size in writing operation)/(disc writing
speed) Flush .times. .times. time = .times. ( cache .times. .times.
size .times. .times. in .times. .times. writing .times. .times.
operation ) / ( disc .times. .times. writing .times. .times. speed
) = .times. 1.5 .times. .times. MB / ( 1.38 .times. .times. MB /
sec . ) = .times. 1086 .times. .times. m .times. .times. sec
##EQU1## Busy .times. .times. time = .times. ( T .times. - .times.
period ) .times. .times. minus .times. .times. ( data .times.
.times. transfer .times. .times. time ) = .times. ( data .times.
.times. size .times. .times. of .times. .times. writing .times.
.times. command ) / ( disk .times. .times. writing .times. .times.
speed ) - .times. ( data .times. .times. size .times. .times. of
.times. .times. writing .times. .times. .times. command ) / ( ATAPI
.times. .times. bus .times. .times. speed ) = .times. 128 .times.
.times. KB / ( 1.38 .times. .times. MB / sec . ) - 128 .times.
.times. KB / ( 16.6 .times. .times. MB / sec . ) = .times. 85.0
.times. .times. m .times. .times. sec ##EQU1.2##
EXAMPLE 2
[0058] As an example of specifying a DVD-RAM drive, the following
parameters may be assumed:
[0059] cache size in writing operation=1 MB
[0060] disc writing speed=2.76 MB/sec.
[0061] seek time=80 msec
[0062] ATAPI bus speed=16.6 MB/sec. (PIO transfer mode 4)
[0063] data size of writing command=256 KB
[0064] from the above specification, the overhead time and the busy
time can be calculated as follows: Flush .times. .times. time =
.times. ( cache .times. .times. size .times. .times. in .times.
.times. writing .times. .times. operation ) / ( disc .times.
.times. writing .times. .times. speed ) = .times. 1 .times. .times.
MB / ( 2.76 .times. .times. MB / sec . ) = .times. 362 .times.
.times. m .times. .times. sec ##EQU2## Busy .times. .times. time =
.times. ( T .times. - .times. period ) .times. .times. minus
.times. .times. ( data .times. .times. transfer .times. .times.
time ) = .times. ( data .times. .times. size .times. .times. of
.times. .times. writing .times. .times. command ) / ( disk .times.
.times. writing .times. .times. speed ) - .times. ( data .times.
.times. size .times. .times. of .times. .times. writing .times.
.times. command ) / ( ATAPI .times. .times. bus .times. .times.
speed ) = .times. 256 .times. .times. KB / ( 1.38 .times. .times.
MB / sec . ) - 256 .times. .times. KB / ( 16.6 .times. .times. MB /
sec . ) = .times. 170 .times. .times. m .times. .times. sec
##EQU2.2##
[0065] Referring again to FIG. 1, in the design of a dynamic
information storage and retrieval system, or the like, of the type
shown that selectively includes both a DVD drive 16 and hard disk
drive 20, the characteristics of the drives 16 and 20 are first
considered. The ATAPI data bus is used to establish efficient
communication. It is noted that the access speed of a hard disk
drive 20 is faster than the access speed of the DVD drive 16. Is
also noted that the DVD drive 16 has a long busy time. From these
considerations, it can be seen that the access schedule to be
asserted by the host device 12 should be made to enable sufficient
access to the hard disk drive 20 while the DVD drive 16 is in its
busy process, as shown in the timing diagram of FIG. 4 to which
reference is now additionally made.
[0066] As shown in the diagram 60 of FIG. 4, the host 12 delivers
data to be recorded to the DVD drive 16 in a recording mode, while,
during the same time frame, receives data from the hard disk drive
20 in a playback mode via the ATA bus 14. As shown in the timing
diagram 62, each "T-period" 34 includes a data transfer period 30
followed by a busy time 32. Simultaneously, during the busy time 32
data is being read back from the hard disk drive 20. This is
accomplished during an initial seek time 64 followed by a plurality
of read cycles 66, 68, . . . . It can be seen that the entire read
cycle is contained within the period that is defined by the busy
period 32 of the DVD drive 16. Moreover, it can be concluded that
the busy time of the DVD drive 16 should be the long enough that
the host can access the hard disk drive 20 during the time that the
DVD drive 16 is in its busy process.
[0067] With reference now additionally to FIG. 5, a graph of busy
time vs. data size of writing command is shown, illustrating the
relationship between data size of the writing command and the busy
time. The seek time of the hard disk drive 20 is assumed to be 100
msec, illustrated by the dashed line 69.
[0068] In the case of a disk writing speed of 1.38 MB/second, shown
by curve 70, the data size of the writing command should be greater
than or equal to 256 KB. In the case of a disk writing speed of
2.76 MB/second, shown by curve 72, the data size of the writing
command should be greater than or equal to 512 KB. It can be seen
that the faster the disk writing speed becomes, the larger the data
size of the writing command needs to be.
[0069] On the other hand, the data size of the writing command
should be less than or equal to the cache size in the writing
operation. If the cache size is small and the disk writing speed is
fast, accessing both the DVD drive and hard disk drive cannot be
realized.
[0070] With reference once again to the diagram of FIG. 3,
according to a preferred embodiment of the present invention, the
host 42 is connected to access the internal controller 56 of the
DVD drive 40, as indicated by the dashed line 49. The access that
is provided to the host 42 allows the host 42 to control the size
of the portion of the internal cache of the storage device 40 that
can be used for writing data to the storage device 40, and to
control the size of the portion of the cache 48 that can be used as
a reading buffer.
[0071] An example of the way that the host device 12 can determine
the cache size in a writing operation (i.e., to enable the host
device 12 to control the overhead time and busy time) is as
follows. Overhead .times. .times. time = .times. seek .times.
.times. time + flush .times. .times. time = .times. seek .times.
.times. time + ( cache .times. .times. size .times. .times. in
.times. .times. writing .times. .times. operation ) / .times. (
disk .times. .times. writing .times. .times. speed ) ##EQU3## busy
.times. .times. time = .times. ( T .times. - .times. period ) - (
data .times. .times. transfer .times. .times. time ) = .times. (
data .times. .times. size .times. .times. of .times. .times.
writing .times. .times. command ) / ( disk .times. .times. writing
.times. .times. speed ) - .times. ( data .times. .times. size
.times. .times. of .times. .times. writing .times. .times. command
) / ( ATAPI .times. .times. bus .times. .times. speed ) <
.times. ( cache .times. .times. size .times. .times. in .times.
.times. writing .times. .times. operation ) / ( disk .times.
.times. writing .times. .times. speed ) - .times. ( cache .times.
.times. size .times. .times. in .times. .times. writing .times.
.times. operation ) / ( ATAPI .times. .times. bus .times. .times.
speed ) ##EQU3.2##
[0072] the seek time, disk writing speed, and ATAPI bus speed are
constant values. Also, the data size of the writing command is less
than or equal to the cache size in the writing operation. It should
be observed that the ability of the host to control the overhead
time and the busy time is of particular advantage in designing a
DVD system.
[0073] With reference again to FIG. 2, which shows the writing and
reading characteristics of a drive that includes a DVD drive, the
host can make the overhead time short, thereby allowing quick
changing of data direction. A large memory in the host to endure
the overhead time is not needed. This makes the system smaller and
simpler than otherwise would be required. On the other hand, in a
system that includes both a DVD drive and a hard disk drive, as
illustrated in FIGS. 4 and 5, to which reference is again made, the
busy time should be long enough that the host can access a hard
disk drive. Even if the disk writing speed is fast, the host can
set a large cache size for its writing operation, thereby selecting
the large data size of the writing command and busy time. Accessing
the hard disk drive while the DVD drive is busy can therefore be
realized.
[0074] Thus, it can be seen that in the design of an information
storage and retrieval system of the type described herein, if the
host has a particular overhead time requirement, the size of the
cache used for writing can be determined from the following
equation: Cache size=(overhead time-seek time).times.disk writing
speed.
[0075] On the other hand, if the host has a particular busy time
requirement, the cache size can be determined from the following
equation: Cache size=busy time.times.(disk writing speed+ATAPI bus
speed)
[0076] Of course, if the host has both overhead and busy time
requirements, both equations can be used to determine an
appropriate cache size.
[0077] Moreover, since the overhead time is the sum of the seek and
flush times, and the overhead time can be controlled, in accordance
with the invention, is it possible to select a cache size that will
completely eliminate the flush time, for example, by making the
overhead time equal to the seek time.
[0078] Although the invention has been described and illustrated
with a certain degree of particularity, it is understood that the
present disclosure has been made only by way of example, and that
numerous changes in the combination and arrangement of parts can be
resorted to by those skilled in the art without departing from the
spirit and scope of the invention, as hereinafter claimed.
* * * * *