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Verifying Images - How many should you submit at a time

JasonRkr
Level 4

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

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Nicolai
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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.

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Nicolai
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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,

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
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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.

Nicolai,

I'm in the NBU Admin Console under the Catalog section.  I vaguely recall being told that the Duplicate function does not Verify an image so the recommendation was to Verify and then, if successful, Duplicate to the other location.

Hmm ... I didn't realize that about MSDP pools.  Maybe I'm not using the correct procedure for what I need to do?  My issue right now is that I have two Disk Pools, A & B.  Disk Pool A is at 95% full and Disk Pool B is at 70% full.  What is the correct procedure to move data from A to B so that I recover space on Disk Pool A?

Thank you,

Jason

X2
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What kind of disk pools are "A & B"? NetBackup will stop writing to a disk pool at 96% full.

To move data: 1) select the images you want to move and duplicate the to the pool B; 2) delete the images from pool A.

PS: if pools A & B are MSDP, gains after deleting images in pool A will depend on the deduplication and may not show untill cleanup is complete. I would move images with lower deduplication ration e.g. containing unique data e..g video, encrypted data.

 

JasonRkr
Level 4

Nicolai and X2,

Thank you both!

Jason