Method for acceleration of storage devices by returning slightly early write status

• US 6,757,767 B1
• Filed: 05/31/2000
• Issued: 06/29/2004
• Est. Priority Date: 05/31/2000
• Status: Expired due to Term

• Current Assignee: Quantum Corporation (Chi Ko Investment Co., Ltd.)
• Original Assignee: Advanced Digital Information Corporation (Chi Ko Investment Co., Ltd.)
• Inventors: Kelleher, Terence M.
• Primary Examiner(s): Dang, Khanh
• Assistant Examiner(s): Huynh, Kim T.
• Application Number:
  US09/583,598
• Time in Patent Office: 1,490 Days
• Field of Search: 710/50, 710/5, 710/107, 710/263, 710/29, 710/310, 710/306, 714/748, 711/156
• US Class Current: 710/107
• CPC Class Codes: G06F 3/0613 in relation to throughput
• CPC Class Codes: G06F 3/0659 Command handling arrangements, e.g. command buffers, queues, command scheduling
• CPC Class Codes: G06F 3/0682 Tape device

Abstract

The present invention features a method for improving data flow from a host initiator on a first data bus to a target tape storage device on a second data bus, both buses being connected to one another by an I/O bridge or gateway. The inventive method allows the I/O bridge to return a slightly early write completion status to the host initiator before data is transmitted to the tape storage device and before the tape write operation is physically complete. The host initiator may then issue additional tape write commands and data may actually be transferred to buffer memory of the I/O bridge or gateway before the first tape write operation has been completed. This improves data throughput between host initiators and target tape storage devices, particularly in a storage area network (SAN).

Claims

1. A method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween, the method comprising:

upon receipt of a first command from an initiator host, determining, at the gateway, whether a deferred error condition has been saved and returning at least a “

check condition”

status to the initiator host, otherwise, issuing a data transfer request command to the initiator host and issuing a write command to the target storage device;

at the gateway, receiving data from the initiator host, and aborting the write command and transmitting predetermined status information to the initiator host if transfer of the data from the initiator host fails;

at the gateway, checking that the target storage device has requested data in response to the write command and, absent a data request, checking for status information from the storage device and aborting the write command absent the status from the target storage device and transmitting status information from the storage device to the initiator host;

when the target storage device has requested data, sending from the gateway the data to the target storage device and, transmitting at least good status to the initiator host;

the target storage device storing the data and transmitting status representative thereof

receiving the status information from the target storage device and, saving deferred status information when the status is not good,

whereby the initiator host receives an early write completed status upon receipt of all the data from the initiator host and independent of transmission of any of the data to the target storage device.

2. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 1, wherein the issuing a data transfer request command to the initiator host and issuing a write command to the target storage device occur substantially simultaneously.

3. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 1, further comprising:

storing the data in a buffer.

4. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 3, wherein the gateway comprises the buffer.

5. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 4, wherein the target storage device comprises a tape storage device.

6. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 3, wherein the early write completed status is returned to the initiator host after the data from the initiator host is stored in the buffer and before transmission of the data from the buffer to the target storage device has begun.

7. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 3, wherein the early write completed status is returned to the initiator host after the data from the initiator host is stored in the buffer and after transmission the data from the buffer to the target storage device has begun.

8. The method for implementing early write completion in a system comprising an initiator host, a target storage device, and a gateway therebetween as recited in claim 3, wherein the data in the buffer is discarded when the target storage device in unable to accept the data.

9. A system for implementing an early write completion status check, comprising:

a) an initiator host operatively connected to a first data bus for originating data to be stored, for transmitting the data on the first data bus, and for receiving status information from the first data bus;

b) a storage device operatively connected to a second data bus and adapted to receive data therefrom, and to transmit status information representative of a predetermined condition of the storage device and a data transfer request on the second data bus; and

c) a bridge device external to, and operatively connected with, the first data bus and the second data bus and adapted to receive the data from the initiator host on the first data bus, and to transmit the data to the target storage device on the second data bus, wherein the bridge device is further adapted to receive the status information from the storage device on the second data bus and for transmitting the status information to the initiator on the first data bus;

wherein the bridge device is further configured to provide the initiator host with an early write completed status from the bridge device prior to completion of transmission of the data to the target storage device and after receiving a data request signal from the target storage device, and wherein data read or write operations for the storage device are not initiated by a bus master; and

wherein the bridge device further comprises a device for receiving status information from the target storage device, creating deferred status information and storing the deferred status information.

10. The system for implementing an early write completion status check as recited in claim 9, wherein the bridge device comprises a buffer for storing the data from the host initiator.

11. The system for implementing an early write completion status check as recited in claim 10, wherein after a predetermined amount of the data from the host initiator is stored in the buffer and the data transfer request has been received from the target storage device, the early write completed status is returned to the initiator host.

12. The system for implementing an early write completion status check as recited in claim 11, wherein after a predetermined amount of the data from the host initiator is stored in the buffer and the data transfer request has been received from the target storage device, the early write completed status is returned to the initiator host before any of the data in the buffer is transmitted to the target storage device.

13. A system for implementing an early write completion status check, comprising:

a) an initiator host operatively connected to a first data bus for originating data to be stored, for transmitting the data on the first data bus, and for receiving status information from the first data bus;

b) a storage device operatively connected to a second data bus and adapted to receive data therefrom, and to transmit status information representative of a predetermined condition of the storage device and a data transfer request on the second data bus; and

c) a bridge device external to, and operatively connected with, the first data bus and the second data bus and adapted to receive the data from the initiator host on the first data bus, and to transmit the data to the target storage device on the second data bus, wherein the bridge device is further adapted to receive the status information from the storage device on the second data bus and for transmitting the status information to the initiator on the first data bus;

wherein the bridge device is further configured to provide the initiator host with an early write completed status from the bridge device prior to completion of transmission of the data to the target storage device and after receiving a data request signal from the target storage device, and wherein data read or write operations for the storage device are not initiated by a bus master; and

wherein the stored deferred status information is transmitted to the initiator host upon receipt of a command therefrom.

14. The system for implementing an early write completion status check as recited in claim 13, wherein the bridge device comprises a buffer for storing the data from the host initiator.

15. The system for implementing an early write completion status check as recited in claim 14, wherein after a predetermined amount of the data from the host initiator is stored in the buffer and the data transfer request has been received from the target storage device, the early write completed status is returned to the initiator host.

16. The system for implementing an early write completion status check as recited in claim 15, wherein after a predetermined amount of the data from the host initiator is stored in the buffer and the data transfer request has been received from the target storage device, the early write completed status is returned to the initiator host before any of the data in the buffer is transmitted to the target storage device.