System for facilitating the copying back of data in disc and tape units of a memory hierarchial system

• US 4,084,231 A
• Filed: 12/18/1975
• Issued: 04/11/1978
• Est. Priority Date: 12/18/1975
• Status: Expired due to Term

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Capozzi, Anthony J., Edson, Bruce A., Cordi, Vincent A.
• Primary Examiner(s): Springborn, Harvey E.
• Application Number:
  US05/642,034
• Time in Patent Office: 845 Days
• Field of Search: 340/172.5, 364/200 MS, 364/900 MS, 445/1
• US Class Current: 711/117
• CPC Class Codes: G06F 12/0866 for peripheral storage systems, e.g. disk cache

Abstract

This is a multi level or hierarchial memory system for a multi processing system in which two or more processing units access the memory system. This memory system has two types of memory units on each level with the exception of the lowest level. One of the types of units is called the data store and is for storing all the data at any given level of the memory. The other type of unit is called the copy back store and is for storing all the changes that have been made in data at that level either by addition or modification. The next to lowest level of the hierarchy the data store and copy back stores are embodied in magnetic disc units and the lowest level of the hierarchy the data stores are embodied in a tape unit with multiple input stations. The disc and tape units are all serially strung together on two independent accessing loops which access the tape unit through a different one of the input stations of the tape unit. In the next to lowest level of the hierarchy, the changes made in data stored on any one of the mentioned disc units are stored on a different one of the mentioned disc units. In the lowest level of the hierarchy, the data base for the memory hierarchy system, is stored in duplicate in the mentioned tape unit. Both duplicate copies of the data base are continually updated for changes made in the data base. The two independent accessing loops are on two different power systems so that changes in data to be transferred into the two lowest levels can continue to be made on one loop while there is a power failure on the other loop.

Claims

1. In a hierarchial memory system made up of a plurality of levels in the hierarchy including a lowest level containing a tape system and a next to lowest level containing disc units, each level with its own data store having a plurality of storage locations for storing data at that level in the hierarchy, an improvement in the means of copying back by a copy back order, into the disc units and tape system of the next to lowest and the lowest levels of the hierarchy, changes of addition or modification made in data stored in the hierarchy by instruction from a processing unit compressing:

a plurality of said disc units in the next to lowest level each with a plurality of actuators each accessing an area of the disc unit, said actuators each being accessible for operation through a plurality of stations,

an archival tape system on the lowest level containing a plurality of tapes said archival system having a plurality of stations each capable of reading or writing data in all said tapes in said archival tape system,

two independently operating loops, one loop joining in series one of the plurality of stations in each of the disc units and the tape system and the other loop forming in series a different one of the plurality of stations in each of the disc units and the tape system,

separate powering means for powering the two loops independently of one another, and

copy back area means in each of two separate ones of said plurality of said disc units, each said copy back area means for containing changes in data stored only in disc units other than the one containing the particular copy back area means whereby loss of one of the powering means does not prevent copying back of data to the tape and disc units using the loop with the operating power supply.

2. The hierarchial memory system of claim 1 wherein said archival tape system includes means for duplicating all the data stored in said archival tape system on two separate tapes of said plurality of tapes when said data is placed in said archival tape system.

3. The hierarchial memory system of claim 1 including buffering means for accumulating changes to be placed into the copy back areas.

4. The hierarchial memory system of claim 3 including means for placing said changes into the buffer in the order in which the data modified by any one of said changes was first modified by any such change that has not been copied into the archival tape system.

5. The hierarchial memory system of claim 3 including means for providing an additional bit of data in entries to the copy back areas to indicate whether or not said entries are valid or not.