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A method to mirror host new modified data with minimum storage space for remote copy suspension

IP.com Disclosure Number: IPCOM000235428D
Publication Date: 2014-Feb-27
Document File: 5 page(s) / 62K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention discloses a method to use minimum free space to automatically backup new modified data after the original remote copy is suspended. Only the host new modified data and out of sync bitmap are copied to the attached machines by new remote copy after suspension. And the new remote copy uses space efficient volume as the secondary volume. Comparing with the normal remote copy, this invention can provide the maximum data redundancy. If the host modified data are lost in primary volume after the original remote copy suspension, the lost data can be restored by the bitmaps and new remote copy secondary volumes in the attached machines. Data redundancy is kept after the suspension and data are protected. Comparing with the multi-target remote copy, this invention needn't large storage space. Only the host new modified data after suspension need to be saved by new remote copy and the space efficient volumes are used. The total size of space efficient volumes is much less than the total size of the remote copy primary volumes. And no permanent storage space is required. If the host modified data are lost in primary volumes after the original remote copy suspension, this invention can restore the lost data as the multi-target remote copy.

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A method to mirror host new modified data with minimum storage space for remote copy suspension


1. BACKGROUND OF THE INVENTION


The suspension of synchronous remote copy or asynchronous remote copy is a very common problem for the disaster recovery configuration of storage subsystems. Remote copy suspension is encountered for many times by users.

Remote copy suspends because of different kinds of problems, while the most common reason is the SAN (Storage Area Network) link issue between the local machine and remote machine. After the suspension, the host modified data only update the remote copy primary volumes and the out of sync bitmap is also updated to record which tracks are modified. After the remote copy resumes, the modified data can be copied from the primary volumes to the secondary volumes. But during the time of remote copy suspension, that's single point of failure. The new modified data are only recorded in the primary volumes. If the data loss happens against the new modified data of primary volumes, the data are permanently lost.

The current solution is to use multi-target remote copy. Multi-target remote copy needs at least 3 machines to establish at least 2 remote copy relationships permanently. And all content of the primary volumes are copied to 2 or more secondary volumes. Additional machines and a lot of storage space are required permanently. A high additional cost is required for the multi-target remote copy. And permanent multi-target remote copy is unnecessary in many situations because synchronous/asynchronous remote copy has provided the 3 site backups.


2. SUMMARY OF THE INVENTION


This invention discloses a method to use minimum free space to automatically backup new modified data after the original remote copy is suspended. Only the host new modified data and out of sync bitmap are copied to the attached machines by new remote copy after suspension . And the new remote copy uses space efficient volume as the secondary volume.

Comparing with the normal remote copy, this invention can provide the maximum data redundancy. If the host modified data are lost in primary volume after the original remote copy suspension, the lost data can be restored by the bitmaps and new remote copy secondary volumes in the attached machines. Data redundancy is kept after the suspension and data are protected.

Comparing with the multi-target remote copy, this invention needn't large storage space. Only the host new modified data after suspension need to be saved by new remote copy and the space efficient volumes are used. The total size of space efficient volumes is much less than the total size of the remote copy primary volumes. And no permanent storage space is required. If the host modified data are lost in primary volumes after the original remote copy suspension, this invention can restore the lost data as the multi-target remote copy.


3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS


Terminology:
Local machine: the...