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Question Malaya Acharya · 5 hr ago

How to do snapshot recovery on a secondary host if IRIS is installed on local OS directory and database and Journal and WIJ are placed on 3 different mounted directory coming from Storage

#InterSystems IRIS

I have installed IRIS community edition on a local directory in Redhat Linux 9.4.

Created a 10G database on a separate mount point directory  which comes out of a storage volume of 50G.

Also placed Journal and WIJ on 2 separate mount point directories  which comes out of two different storage volume of 50G each.

I want to take a snapshot and recover the snapshot on a secondary host and check the consistency of the database. 

As Storage snapshot will be taken, only Data, Journal and WIJ file placed on Storage volumes will be snapshotted.

Let me know what is the process of recovering the snapshot data in secondary.

As per my understanding, We only can mount the database, journal and WIJ on secondary. We do not need to start the instance in the secondary. So WIJ and Journal will not be of any use.  

So I am confused if this is the recommended configuration? How customer build their environment ? and what would be the correct way to recover snapshot data ?

Thanks in advance for the assistance.

Product version: IRIS 2025.2
$ZV: IRIS_Community-2025.2.0.227.0-lnxrh9x64.tar.gz
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DC AI Bot · 4 hr ago Bot

Recovering from a storage snapshot on a secondary host with the setup described involves several considerations to ensure database integrity and consistent functionality.

  1. Snapshot Requirements: A valid snapshot for recovery must include the database, journal files, the WIJ (Write Image Journal), and optionally the installation directory if an entire instance recovery is needed 123.

  2. Recovery Procedure:

    • Mount the Snapshot: Mount the snapshot volumes (database, journal, and WIJ directories) onto the secondary host.
    • Verify Contents: Ensure that all files (database, journal, and WIJ) are intact and properly mounted.
    • Perform Recovery:
      • Use journal files to roll forward or rollback transactions to maintain data integrity. The journal files must be applied even if no new changes occurred after the snapshot to ensure uncommitted transactions at the snapshot time are rolled back 123.
      • Typically, InterSystems IRIS handles physical and logical integrity checks during startup using WIJ and journals, if the snapshot is complete.

  3. Journals and WIJ:

    • Journals restore updates from the last backup to snapshot time and provide transactional integrity through rollback of incomplete transactions 123.
    • WIJ maintains consistency during crash recovery, ensuring all buffers are written to the database 23.

  4. Recommended Configuration:

    • For optimal recoverability and performance, system components should be separated across distinct physical or logical storage devices:
      • Separate primary and alternate journal directories.
      • Use different storage devices for database and journal directories as well as WIJ files to prevent single points of failure 41.
    • Avoid using symbolic links for database directories for reliability 4.

  5. Testing and Best Practices:

    • Regularly test disaster recovery procedures, including snapshot restores, journal applications, and running simulated activity on the secondary to ensure integrity 3.
    • Perform integrity checks after mounting snapshots to validate database structures 1.

If your configuration excludes certain components from the snapshot, it might compromise recovery or data consistency. Including all key parts in a snapshot is critical for a consistent and successful recovery procedure.


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