Electrical computers and digital data processing systems: input/ – Intrasystem connection – Bus access regulation
Reexamination Certificate
1998-04-30
2001-04-24
Auve, Glenn A. (Department: 2781)
Electrical computers and digital data processing systems: input/
Intrasystem connection
Bus access regulation
C710S033000
Reexamination Certificate
active
06223235
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data server and, more particularly, to a data server having a packet token generator that facilitates the delivery of data at any data rate within a wide range of data rates such that data rate error and packet timing jitter are acceptable.
BACKGROUND OF THE INVENTION
A hard disk based data server offers high speed random data accessing capability which is useful, for example, in digital video applications such as interactive video processing, non-linear video editing test video stream generation, and the like. The data servers that have been developed in the past for these applications primarily involve the use of the SCSI protocol because the SCSI protocol has many advantages including compatibility, expandability, and exchangeability. However, these data servers have been either low speed, low cost data servers, or high speed, high cost data servers.
A typical data server
10
implementing the SCSI protocol is illustrated in FIG.
1
. The data server
10
includes an SCSI disk
12
for storing data which must be accessed and processed by an application
14
. The application
14
accesses the data stored on the SCSI disk
12
through a host computer
16
and an SCSI bus adapter
18
. The host computer
16
communicates with the SCSI bus adapter
18
over a host bus
20
, and the SCSI bus adapter
18
is connected to the SCSI disk
12
by way of an SCSI bus
22
.
One typical requirement demanded for the design of the data server
10
is that the host computer
16
, the SCSI bus adapter
18
, and the host bus
20
be able to handle the data flow at substantially the same data rates of the SCSI disk
12
and the application
14
. While this requirement is technically feasible when the data rate is high, satisfying this requirement at high data rates results in the data server
10
being complicated and costly.
Moreover, unless the data server
10
is highly complicated, the data server
10
is not flexible, simple, or fast, because only the SCSI bus adapter
18
communicates with the SCSI disk
12
. For example, as the application
14
processes data stored on the SCSI disk
12
, it repeatedly starts and stops data flow from the SCSI disk
12
because the SCSI disk
12
delivers data at a rate which is faster than the processing rate of the application
14
. However, all start and stop instructions from the application
14
must be passed to the SCSI disk
12
through the host computer
16
and the SCSI bus adapter
18
, which tends to slow down data transfer.
Furthermore, the application
14
may issue data requests at a frequency which is higher than the required data transfer rate of the data file on the SCSI disk
12
. The data server
10
must be able to compensate for the difference between the frequency of the data requests from the application
14
and the data transfer rate of the data file on the SCSI disk
12
.
Accordingly, the present invention is directed to a packet token generator which achieves these performance requirements. The data server based on the present invention is fast, flexible and/or low cost compared to prior art data servers, particularly to prior art video servers.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, a data server comprises a storage disk, an SCSI bus, an SCSI bus adapter connected to the SCSI bus, a host computer, and an application. The storage disk stores data. The SCSI bus is connected to the storage disk and is arranged to transfer the data from the storage disk. The host computer is arranged to control the SCSI bus adapter. The application is connected to the SCSI bus, and the application is arranged to receive the data transferred by the SCSI bus and to control the transfer of the data from the storage disk.
In accordance with another aspect of the present invention, an SCSI data server comprises an SCSI memory, an SCSI bus connected to the SCSI memory, an SCSI controller, and an application. The SCSI memory stores data. The SCSI controller is connected to the SCSI bus and is arranged to initiate transfer of the data from the SCSI memory. The application is connected directly to the SCSI bus, and the application is arranged to use the data transferred over the SCSI bus and to control the transfer of the data from the SCSI memory after the transfer of the data has been initiated by the SCSI controller.
In accordance with yet another aspect of the present invention, a data server comprises a storage disk, an SCSI bus, an SCSI bus adapter connected to the SCSI bus, a host computer, and an application. The storage disk stores data. The SCSI bus is connected to the storage disk and is arranged to transfer the data from the storage disk. The host computer is arranged to control the SCSI bus adapter. The application is connected to the SCSI bus, and the application includes a switch arranged to switch control of the SCSI bus from the SCSI bus adapter to the application. The application includes a data rate controller arranged to control the rate at which data is transferred from the SCSI disk to the application.
REFERENCES:
patent: 5881245 (1999-03-01), Thompson
Auve Glenn A.
Zenith Electronics Corporation
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