Data mirroring method

Abstract

A copy source device includes bit map acquisition and bit map merge functions. In accordance with bit-map management information in which a bit map indicating the presence of written data is rounded, the bit map acquisition and bit map merger acquires required bit map from a copy destination device, and merges the acquired bit map to a corresponding bit map of the copy source device. The copy destination device includes bit-map management information updater. The bit-map management information updater updates bit-map management information indicating a write operation when the write operation has been performed during a copy suspend mode. During a copy resume mode, the copy source device requests the copy destination device to transfer the bit-map management information, and in response, the copy destination device transfers the bit-map management information.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram indicating a sequence of acquiring a bit-map management information of one embodiment of the present invention;

FIG. 2 is a functional block diagram of one embodiment of the present invention;

FIG. 3 illustrates a bit map and a management status of management information thereof, in accordance with one embodiment of the present invention;

FIG. 4 illustrates the management of a location where data is written according to an embodiment of the present invention;

FIG. 5 illustrates how bit-map management information is acquired according to an embodiment of the present invention;

FIGS. 6A and 6B illustrate a merge status responsive to the bit-map management information according to an embodiment of the present invention;

FIG. 7 illustrates a process flow during a copy/backup suspend mode according to an embodiment of the present invention;

FIG. 8 illustrates a write operation on a copy destination device during the suspend mode according to an embodiment of the present invention;

FIG. 9 illustrates a process flow of a copy resume command according to an embodiment of the present invention;

FIG. 10 illustrates a merge process only task according to an embodiment of the present invention;

FIG. 11 illustrates a process flow of a merge process determination according to an embodiment of the present invention;

FIG. 12 illustrates formats of a session management table, bit map, and control table of the bit map according to an embodiment of the present invention;

FIG. 13 illustrates a first known example; and

FIG. 14 illustrates a second known example.

Claims

1. An apparatus, comprising: a first storage device to store user data and comprising:a controller to control the first storage device according to a process comprising:maintaining bit-map information indicative of locations of updated portions of the user data;maintaining rounded bit-map information indicative of portions of said bit-map information indicating the locations of said updated portions;a second storage device, comprising:a controller to control the second storage device according to a process comprising:maintaining a copy bit-map information indicative of locations of the user data to be copied;copying the user data based upon the copy bit-map information to the first storage device;receiving the rounded bit-map information maintained in the first storage device, upon receiving a copy resume command to resume the copying;acquiring a portion of said bit-map information maintained in the first storage device, based upon the rounded bit map information; andupdating the copy of the user data by accessing a location of the user data in the first storage device as indicated by the portion of the acquired bit-map information for synchronization of the copy of the user data with the user data in the first storage device.

2. The apparatus according to claim 1, wherein the process of the second storage device controller further comprises: receiving a copy suspend command to suspend the copying prior to the receiving of the copy resume command.

3. The apparatus according to claim 1, wherein the process of the first storage device controller further comprises: selecting whether to process the bit map through a bit-map process or a bit-map management information transmission process.

4. A storage device storing one set of information data which is to be in synchronization with that of other storage device, the storage device comprising: first bit-map information management means for maintaining bit-map information indicative of locations of updated portions of the user data;second bit-map information management means for maintaining rounded bit-map information indicative of portions of said bit-map information indicating the locations of said updated portions;means for acquiring the rounded bit-map information maintained in the other storage device, and based upon the acquired rounded bit-map information, acquiring a portion of said bit-map information maintained in the other storage device; andmeans for updating the user data by accessing the locations of the user data indicated by the portion of the acquired bit-map information for synchronization of the user data.

5. A storage device storing one set of user data which is to be in synchronization with that of other storage device, the storage device comprising: a controller to control the storage device according to a process comprising:clearing a bit map in the copy destination device during a suspend mode;maintaining bit-map information indicative of locations of updated portions of the user data;maintaining rounded bit-map information indicative of portions of said bit-map information indicating the location of said updated portions;acquiring the rounded bit-map information maintained in the other storage device, and based upon the acquired rounded bit-map information, acquiring the portion of said bit-map information maintained in the other storage device; andupdating the user data by accessing the location of the user data indicated by the portion of the acquired bit-map information for synchronization of the user data.

6. The storage device according to claim 5, wherein the process of the controller further comprises generating the bit-map information as a bit-map table of rows and columns, and generating the rounded bit-map information indicating updates in the bit-map table on a per row basis of the bit-map information table.

7. A storage method storing one set of information data which is to be in synchronization with that of other storage device, the storage method comprising the steps of: maintaining bit-map information indicative of locations of updated portions of the user data;maintaining rounded bit-map information indicative of portions of said bit-map information indicating the locations of said updated portions;acquiring the rounded bit-map information maintained in the other storage device, and based upon the acquired rounded bit-map information, acquiring a portion of said bit-map information maintained in the other storage device; andupdating the user data by accessing the locations of the user data indicated by the portion of the acquired bit-map information for synchronization of the user data.

8. A computer-readable recording medium that stores a computer program for storing one set of information data which is to be in synchronization with that of other storage device by controlling a storage device according to a process comprising: maintaining bit-map information indicative of locations of updated portions of the user data;maintaining rounded bit-map information indicative of portions of said bit-map information indicating the locations of said updated portions;acquiring the rounded bit-map information maintained in the other storage device, and based upon the acquired rounded bit-map information, acquiring a portion of said bit-map information maintained in the other storage device; andupdating the user data by accessing the locations of the user data indicated by the portion of the acquired bit-map information for synchronization of the user data.