Buffered peripheral system and method for backing up and retrieving data to and from backup memory device

• US 5,193,154 A
• Filed: 10/25/1991
• Issued: 03/09/1993
• Est. Priority Date: 07/10/1987
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Yamamoto, Akira, Doi, Takashi, Nozawa, Masafumi, Kitajima, Hiroyuki
• Primary Examiner(s): Fleming, Michael R.
• Assistant Examiner(s): Ray, Gopal C.
• Application Number:
  US07/783,718
• Time in Patent Office: 501 Days
• Field of Search: 395/250, 395/425, 395/275, 395/800, 371/40.1, 371/40.2, 371/10.1, 365/189.05, 364/200 MS File, 364/900 MS File
• US Class Current: 714/6.1
• CPC Class Codes: G06F 13/00 Interconnection of, or transfer of information or other signals between, memories, input/output devices or central processing units interface circuits for specific input/output devices G06F3/00 ; multiprogram control therefor G06F9/46; multiprocessor systems G06F15/16
• CPC Class Codes: Y10S 707/99955 Archiving or backup

Abstract

A buffered peripheral system comprises a backup memory and a primary control unit which has a buffer memory for temporarily storing a copy of the contents of a buffer memory which stores data to be written to a peripheral device and a control device for issuing a command necessary to write the block stored in the buffer memory device to the peripheral device. The primary control unit also includes a recording device for recording the block number corresponding to the block which was most recently written to the peripheral device. The blocks of data which have been written to the peripheral device is then deleted from the backup memory to make room for storing further blocks of data. The system further has a backup control unit substantially identical to the primary control unit. Only the primary control unit normally operates to control the writing to the peripheral device. Upon detection of the failure of the buffer memory in the primary control unit, the backup control unit completes the operation of writing to the peripheral device by retrieving the blocks of data to be written to the peripheral device from the backup memory device using the block number information.

Claims

1. A buffered peripheral system which is connected to a central processing unit through a channelling means, comprising:

a peripheral device;

a backup memory means for storing blocks of data written by said central processing unit, which are to be written to said peripheral device in accordance with a command from said central processing unit;

a control unit, connected between said channelling means and said peripheral device, said control unit further comprising a buffer memory means for temporarily storing the block of data which is to be written to said peripheral device a recording means for recording a block number corresponding to a most recently written block of data in said peripheral device from said buffer memory means, and said control unit comprising a control means for issuing a command necessary to write said block of data stored in the buffer memory means to said peripheral device, including the block number associated with the block of data stored in said buffer memory means; and

means for deleting the block of said which has been previously written to said peripheral device from said backup memory means.

2. A buffered peripheral system according to claim 1, wherein said central processing unit comprises a main memory means and said backup memory means is included in said main memory means.

3. A buffered peripheral system according to claim 1, wherein said central processing unit reads the block number recorded in said recording means at predetermined time intervals and deletes the blocks of data stored in said backup memory means whose block number is less than the block number recorded in said recording means to make room for subsequent blocks of data to be written to said peripheral device.

4. A buffered peripheral system according to claim 1, wherein said central processing unit sends, at predetermined time intervals, an information indicative of the block number of a desired one of blocks stored in said backup member means to said control unit said control unit compares the desired block number with the block number stored in said recording means and sends a signal to said central processing unit indicative of whether the block number recorded in said recording means is greater than or equal to the desired block number stored in backup memory means, and only if said block number recorded in said recording means is greater than or equal to, said central processing unit deletes the blocks of data corresponding to the block numbers that are less than the desired block number from the backup memory means.

5. A method of backing up a buffered peripheral system which is connected to a central processing unit, wherein said buffered peripheral system includes primary and back-up control units and a backup memory means to store blocks of data to be written to a peripheral device, said primary and back-up control units having a buffer memory means for temporarily storing a block of data, each of said first and second control units comprising a control means for issuing a command necessary to write the block of data stored in said buffer memory means to said peripheral device, including a block number associated with the block of data stored in said buffer memory means and a recording area for recording the block number corresponding to a most recently written block of data to said peripheral device from said buffer memory means, said buffer memory means being used for storing a copy of the contents of said backup memory means, said method comprising the steps of:

(a) detecting a fault in said buffer memory in said primary control unit;

(b) determining whether the content of said recording means can be read out from said buffer memory in said primary control unit; and

(c) carrying out one of first and second processings, the first processing being carried out when the contents of said recording means can be read out, said first processing including the sub-steps of;

(i) reading out the block number corresponding to a most recently written block of data to said peripheral device;

(ii) changing said primary control unit that is in fault over to said back-up control unit;

(iii) writing blocks of data which are stored in said backup memory means and which correspond to subsequent block numbers following the block number recorded in said recording means, to said peripheral device through said back-up control unit; and

(iv) deleting the blocks of data corresponding to the block number recorded in said recording means and block numbers preceding said block number recorded in said recording means, from said backup memory means;

(d) said second processing being carried out when the content of said recording means cannot be read out, said second processing including the sub-steps of;

(i) changing said primary control unit that is in fault over to said back-up control unit;

(ii) determining the block number which corresponds to a most recently written block of data to said peripheral device;

(iii) writing the blocks of data which are stored in said backup memory means and which correspond to subsequent block numbers following the block number recorded in said recording means, to said peripheral device through said back-up control unit; and

(iv) deleting the blocks of data corresponding to the block number recorded in said recording means and block numbers preceding said block number recorded in said recording means, from said backup memory means.