System and method for transferring compressed and uncompressed data between storage systems

• US 5,630,092 A
• Filed: 01/02/1996
• Issued: 05/13/1997
• Est. Priority Date: 10/20/1994
• Status: Expired due to Fees

• Current Assignee: International Business Machines SA (International Business Machines Corporation)
• Original Assignee: International Business Machines SA (International Business Machines Corporation)
• Inventors: Carreiro, Paul P., Nowlen, David R., Fish, Robert R.
• Primary Examiner(s): Swann, Tod R.
• Assistant Examiner(s): Thai, Tuan V.
• Application Number:
  US08/581,719
• Time in Patent Office: 497 Days
• Field of Search: 395/404, 395/431, 395/438, 395/439, 395/600, 395/888, 364/DIG. 1, 364/DIG. 2, 364/404, 364/431, 364/438, 364/439, 364/600, 364/715.02, 364/951.3
• US Class Current: 711/111
• CPC Class Codes: G06F 11/1448 Management of the data involved in backup or backup restore
• CPC Class Codes: G06F 2003/0697 device management, e.g. handlers, drivers, I/O schedulers
• CPC Class Codes: G06F 3/0601 Interfaces specially adapted for storage systems

Abstract

A system and method are provided for sharing a data stream between a first data storage system in communication with a second data storage system. Meta-data is associated with each record of the data stream. Zero or more records of the data stream are compressed at the first storage system. The meta-data for the compressed data record is updated to indicate that the data record has been compressed. The data stream including the compressed data record with the updated meta-data is sent to the second storage system. The meta-data and the data stream records are stored on a storage device at the second data storage system.

Claims

1. A method for sending a data stream of data records received from a host system between a first and second storage system in communication with each other and each storage system in communication with at least one host system, each storage system including a memory, a processor, at least one storage device, means for communicating with another storage system, means for storing data records on the included storage device and means for transferring a data stream to and from said host system, said method comprising the steps of:

(a) storing in said first storage system meta-data about each data record including whether a data record is compressed;

(b) compressing at said first storage system without assistance from the host system or the second storage system, at least one data record in the data stream, and updating the meta-data for a data record that has been compressed to indicate that the data record is compressed;

(c) sending the data stream with the meta-data from the first storage system to the second storage system;

(d) storing the meta-data and data stream on a storage device at the second storage system;

(e) reading the meta-data at the second storage system that at least one data record in the data stream has been compressed;

(f) storing as part of the meta-data the length of the data record when compressed and the length of the data record when non-compressed, and wherein both compressed and non-compressed data records are transmitted as part of the data stream; and

(g) in response to a request from a host system to the second storage system for the data stream, the second storage system retrieving the data stream from the storage device, uncompressing any compressed records in the data stream without assistance from the host system or the first storage system, and sending the data stream of non-compressed data records to the requesting host system.

2. The method of claim 1 wherein the second storage system identifies the presence of a compressed record.

3. The method of claim 1 further comprising the step of the second storage system sending the data stream including a compressed data record to a third storage system having a storage device, where the third storage system is unaware of the presence of the compressed record and stores the data stream on a storage device controlled by the third storage system.

4. The method of claim 1 wherein a host system transfers data to the first storage subsystem in an non-compressed state.

5. A method for sending a data stream stored at a second storage system as provided in claim 1 to a third storage system comprising the further steps of:

(a) reading the data records from the storage device controlled by the second storage system;

(b) identifying from the meta data stored with the data records which records are compressed;

(c) decompressing any compressed records; and

(d) sending the data records in a non-compressed state to the third storage system.

6. The method of claim 1, further comprising the steps of sending a data stream between a first and second storage systems wherein no data record in the data stream is compressed.

7. A system for sharing a data stream of data records between a first and second storage system in communication with each other and each storage system wherein both compressed and non-compressed data records are transmitted as part of the data stream in communication with at least one host system, each storage system including at least one storage device having a plurality of data records stored on the storage device, said system comprising:

means for associating with at least one data record stored on the first storage system a record length indicator;

compression means for compressing and decompressing at least one data record at the first storage system independent of the host system and the second storage system;

means for associating with a compressed data record stored on the first storage system a compressed data record length indicator;

means for sending the data stream including the compressed data record with the record length indicator and a compressed record length indicator from the first storage system to the second storage system;

means for storing the compressed data record and indicators on a storage device at the second storage subsystem;

means for retrieving a data record from a storage device at the second storage system;

means for identifying a compressed data record, at the second storage system independent of the first storage system and the host system

means for decompressing the compressed data record at the second storage system independent of the first storage system and the host system; and

means for sending a data stream to a requesting host system directly from the second storage system independent of the first storage system and the host system;

means for transferring the data stream from the second storage system to a third storage system wherein all data records in the data stream are in a non-compressed state,

means for transferring a data record from the second storage system to the third storage subsystem in a compressed state wherein the third storage subsystem is unaware of the compressed state and stores the data record on a storage device controlled by the third storage system independent of the first and the second storage system and the host system.