Forum Discussion

JasonRkr's avatar
JasonRkr
Level 4
3 years ago

Verifying Images - How many should you submit at a time

Is there a limit to the number of image verifications you should run at any one time?  I have a SQL Server backup that generates almost 200 images.  I want to verify them and then, if successful, duplicate them to another media server.

I'm running NetBackup 7.7.3 and before you mention it, yes, I know it's old and I am working on the upgrade.  :)

Thank you,

Jason

Linux
  • Nicolai's avatar
    Nicolai
    3 years ago

    Hi JasonRkr 

    I think you can use all of your Netbackup ressources for verification. It works pretty much like backups.

    But I am not sure verification add any value, since all modern tape drives does read after write. And  you could say a duplication is the same as a verification.

    https://en.wikipedia.org/wiki/Linear_Tape-Open

    Also, when data is written to the tape it is verified by reading it back using the read heads that are positioned just "behind" the write heads. This allows the drive to write a second copy of any data that fails the verify without the help of the host system.

  • Nicolai's avatar
    Nicolai
    Moderator
    3 years ago

    Hi JasonRkr 

    I think you can use all of your Netbackup ressources for verification. It works pretty much like backups.

    But I am not sure verification add any value, since all modern tape drives does read after write. And  you could say a duplication is the same as a verification.

    https://en.wikipedia.org/wiki/Linear_Tape-Open

    Also, when data is written to the tape it is verified by reading it back using the read heads that are positioned just "behind" the write heads. This allows the drive to write a second copy of any data that fails the verify without the help of the host system.

    • JasonRkr's avatar
      JasonRkr
      Level 4
      3 years ago

      Nicolai,

      Thank you for the information.  At this point, we're not writing to tape and I didn't think the duplication process verified images before copying.  I'll have to read that section again.  

      Jason

      • Nicolai's avatar
        Nicolai
        Moderator
        3 years ago

        Well, its pretend on what kind of verify you are looking for. Can you please elaborate on this ?

        The process of duplicating a image moves data to another. If the image is damaged or missing it's highly likely duplication will fail. If replication is between MSDP pool, the moved data is actual only unique finger prints, not the entire dataset. MSDP does it own data integrity checking, pls see:

        https://www.veritas.com/support/en_US/doc/25074086-127355784-0/v62562350-127355784

        Verifying a backup image from a database host is impossible, databases and always live and changes are written to the databases all the time. Most databases engines can however perform a integrity checking before backup, but it is very ressource expensive.