US 5,742,792 A · Remote data mirroring

Abstract

Two data storage systems are interconnected by a data link for remote mirroring of data. Each volume of data is configured as local, primary in a remotely mirrored volume pair, or secondary in a remotely mirrored volume pair. Normally, a host computer directly accesses either a local or a primary volume, and data written to a primary volume is automatically sent over the link to a corresponding secondary volume. Each remotely mirrored volume pair can operate in a selected synchronization mode including synchronous, semi-synchronous, adaptive copy - remote write pending, and adaptive copy - disk. Direct write access to a secondary volume is denied if a "sync required" attribute is set for the volume and the volume is not synchronized. If a "volume domino" mode is enabled for a remotely mirrored volume pair, access to a volume of the pair is denied when the other volume is inaccessible. In a "links domino" mode, access to all remotely mirrored volumes is denied when remote mirroring is disrupted by an all-links failure. The domino modes can be used to initiate application-based recovery, for example, recovering a secondary data file using a secondary log file. In an active migration mode, host processing of a primary volume is concurrent with migration to a secondary volume. In an overwrite cache mode, remote write-pending data in cache can be overwritten. Write data for an entire host channel command word chain is bundled in one link transmission.

Claims38

Dependent claims

A system for automatically providing remote copy data storage, said system comprising:

a host computer;
a first data storage system including at least a first data storage system controller and at least one data storage device, said first data storage system being coupled to said host computer for storing data to be accessed by at least said host computer;
a second data storage system including at least a second data storage system controller and at least one data storage device, said second data storage system being remotely coupled to said first data storage system for copying of said data to said second data storage system controller;
and
said first data storage system controller coordinating and controlling the copying of said data to said second data storage system controller wherein said first data storage system maintains an index, said index including at least a first indicator providing an indication of whether a predetermined data element stored on said first data storage system is valid, a second indicator providing an indication of whether said predetermined data element stored on said second data storage system is valid, a third indicator providing an indication of whether a write is pending to said predetermined data element stored on said first data storage system, and at least a fourth indicator providing an indication of whether a write is pending to said predetermined data element stored in said second data storage system.

2 more elements

A data storage system for providing remote data copying to remote data storage, said data storage system comprising:

primary data storage for storing a primary copy of data;
and
a data storage controller for controlling storage of data in said primary data storage and transmission of data over a link from said data storage system to said remote data storage to store a secondary copy of the data in said remote data storage;
wherein said data storage system maintains an index, said index including at least a first indicator providing an indication of whether a predetermined data element stored on said data storage system is valid, a second indicator providing an indication of whether said predetermined data element stored in said remote data storage is valid, a third indicator providing an indication of whether a write is pending to said predetermined data element stored on said data storage system, and at least a fourth indicator providing an indication of whether a write is pending to said predetermined data element stored in said remote data storage.

1 more element

A method of operating a data storage system for providing remote data copying to remote data storage, said data storage system having primary data storage for storing a primary copy of data, and a data storage controller for controlling storage of data in said primary data storage and transmission of data over a link from said data storage system to said remote data storage to store a secondary copy of the data in said remote data storage, said method comprising:

maintaining, in storage of said data storage system, a first indicator providing an indication of whether a predetermined data element stored on said data storage system is valid;
maintaining, in said data storage system, a second indicator providing an indication of whether said predetermined data element stored in said remote data storage is valid;
maintaining, in said data storage system, a third indicator providing an indication of whether a write is pending to said predetermined data element stored on said data storage system;
and
maintaining, in said data storage system, a fourth indicator providing an indication of whether a write is pending to said predetermined data element stored in said remote data storage.

2 more elements

A program storage device readable by a data storage system, said program storage device encoding a program for execution by the data storage system for providing remote data copying from the data storage system to remote data storage, wherein the program is executable by the data storage system for maintaining an index, said index including at least a first indicator providing an indication of whether a predetermined data element is valid in storage of the data storage system, a second indicator providing an indication of whether said predetermined data element is valid in said remote data storage, a third indicator providing an indication of whether a write of said predetermined data element is pending to storage of the data storage system, and at least a fourth indicator providing an indication of whether a write of said predetermined data element is pending to said remote data storage.

A system for automatically providing remote copy storage of data from a host computer, said system comprising:

a first data storage system for coupling to the host computer for storing data from the host computer;
and
a second data storage system remotely coupled to the first data storage system for receiving a copy of the data from the first data storage system;
wherein the first data storage system is adapted to operate in an asynchronous mode wherein data is copied from the first data storage system to the second data storage system asynchronously from the time when the first data storage system returns an i/o completion signal for the data to the host computer, and the first data storage system maintains, in the first data storage system, an index of information about the data as stored in the first data storage system and about the copy of the data as stored in the second data storage system, the index identifying data stored in the first data storage system and not yet copied to the second data storage system, the index including additional information about the copy of the data stored in the second data storage system so that the additional information is accessible by the first data storage system without retrieval from the second data storage system in order to reduce time for recovery from a failure to access the data stored in the first data storage system.

1 more element

A system for automatically providing remote copy data storage, said system comprising:

a host computer;
a first data storage system coupled to the host computer for storing data from the host computer;
and
a second data storage system remotely coupled to the first data storage system for receiving a copy of the data from the first data storage system;
wherein the first data storage system is adapted to operate in an asynchronous mode wherein data is copied from the first data storage system to the second data storage system asynchronously from the time when the first data storage system returns an i/o completion signal for the data to the host computer, and the first data storage system maintains, in the first data storage system, an index of information about the data as stored in the first data storage system and about the copy of the data as stored in the second data storage system, the index identifying data stored in the first data storage system and not yet copied to the second data storage system, the index including additional information about the copy of the data stored in the second data storage system so that the additional information is accessible by the first data storage system without retrieval from the second data storage system in order to reduce time for recovery from a failure to access the data stored in the first data storage system.

2 more elements

A method of operating a system for automatically providing remote copy storage of data from a host computer, the system having a first data storage system coupled to the host computer for storing the data from the host computer, and a second data storage system remotely coupled to the first data storage system for receiving a copy of the data from the first data storage system, said method comprising the steps of:

operating the first data storage system in an asynchronous mode wherein data is copied from the first data storage system to the second data storage system asynchronously from the time when the first data storage system returns an i/o completion signal for the data to the host computer, and the first data storage system maintains, in the first data storage system, an index of information about the data as stored in the first data storage system and about the copy of the data as stored in the second data storage system, the index identifying data stored in the first data storage system and not yet copied to the second data storage system, the index including additional information about the copy of the data stored in the second data storage system;
and
in response to a failure to access the data stored in the first data storage system, the first data storage system accessing the additional information stored in the index in the first data storage system in order to reduce time for recovery from the failure.

Dependencies are inferred from the claim text.

Remote data mirroring

Life of this patent

Remote data mirroring

Life of this patent

Abstract

Claims38