US 6,173,377 B2Granted

Remote data mirroring

AssigneeEMC Corporation

InventorsMoshe Yanai, Natan Vishlitzky, Bruno Alterescu, Daniel D. C Castel, Gadi G Shklarsky, Yuval Ofek

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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.

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

a first data storage subsystem including first data storage, and
a second data storage subsystem including second data storage, the second data storage subsystem being at a location remote from the first data storage subsystem, and
at least one data link between the first data storage subsystem and the second data storage subsystem for transmission of remote copy data from the first data storage subsystem to the second data storage subsystem, and for transmission of remote copy data from the second data storage subsystem to the first data storage subsystem;
wherein the first data storage includes a first set of primary storage locations, and the second data storage includes a first set of secondary storage locations corresponding to the first set of primary storage locations;
and the second data storage includes a second set of primary storage locations, and the first data storage includes a second set of secondary storage locations corresponding to the second set of primary storage locations;
and
wherein said first data storage subsystem maintains a first indicator providing an indication of whether a first specified data element stored in said first set of primary data storage locations is valid, a second indicator providing an indication of whether a valid secondary copy of said first specified data element is stored in said first set of secondary data storage locations, a third indicator providing an indication of whether a write is pending of said first specified data element to said first set of primary data storage locations, and at least a fourth indicator providing an indication of whether a write is pending of said first specified data element to said first set of secondary data storage locations, and
wherein said second data storage subsystem maintains a fifth indicator providing an indication of whether a second specified data element stored in said second set of primary data storage locations is valid, a sixth indicator providing an indication of whether a valid secondary copy of said second specified data element is stored in said second set of secondary data storage locations, a seventh indicator providing an indication of whether a write is pending of said second specified data element to said second set of primary data storage locations, and at least an eighth indicator providing an indication of whether a write is pending of said second specified data element to said second set of secondary data storage locations.

5 more elements

Facts

Application

09/061,708Filed 17 Apr 1998 · continuation

Priority

23 Apr 1993

Granted

9 Jan 2001

Term ends

Not estimatedThe source records don’t support an estimate.

Classification24 codes

G06F 11/2071
By mirroring: using a plurality of controllers
G06F 3/0601
Digital input from, or digital output to, record carriers , e.g. RAID, emulated record carriers or networked record carriers: interfaces specially…
G06F 3/0608
Specifically adapted to achieve a particular effect: saving storage space on storage systems
G06F 3/061
Specifically adapted to achieve a particular effect: improving I/O performance

Family

Application08/052,239Parent of this continuation-in-part · filed 23 Apr 1993

Application08/654,511Parent of this continuation · filed 28 May 1996

US 5,544,347 AParent of this continuation-in-part · filed 6 Aug 1996

US 5,742,792 AParent of this continuation

Application08/654,511Parent of this continuation-in-part

US 5,292,182 ARelated patent

US 6,173,377 B2This patent

From the US filing history. Foreign family members aren’t listed.

Abstract

Claims12