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Commserve LiveSync in a HSX environment

  • 11 April 2023
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PedroRocha
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Hello all,

I just hit a situation. When trying to change the LiveSync default storage policy, documentation told me that the new user defined storage policy for the commserve livesync feature should be NON deduplicated.

Happens that this environment has as storage options an HSX RA appliance and tape storage.

HSX RA is per design a deduplicated storage pool.

Has any one faced this situation? I did not want to create another disk pool to satisfy this NON deduplication necessity. Is there any way out?

Regards,

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Best answer by Chris Hollis 13 April 2023, 00:59

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Pedro

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O
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You can not remove deduplication from an already created storage pool so you will have to create the new pool.

PedroRocha
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You can not remove deduplication from an already created storage pool so you will have to create the new pool.

Hello,

I understand that.

But considering this environment has only a HSX as disk backup destination.. what should I do? Customer does not want to create a new area to provision this.

Should we quit LiveSync for that reason?

Regards,

Pedro
Chris Hollis
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@PedroRocha 

We do not recommend that you use a dedupe policy. This doesn’t mean to say that you can’t, but you’ll likely encounter problems down the line and we would consider this a ‘not supported’ configuration.
 

Why? The reason for this is that, for CS LiveSync, we are mostly backing up sql transaction logs which cannot be deduplicated (anyway) and if a fail over occurs, a deduplication resync will have to occur first, before any further transaction log backups are able to run again.

 

In this case, if there are deduplication database issues, like the DDB not being online for any reason, the transaction logs will not run. This DDB dependency reduces backup resiliency. 


This is the main reason why we recommend non deduplication storage policy to be associated.

If the customer doesn’t want to provision this, then LiveSync may not be a solution for them.

Regards,

Chris

 

PedroRocha
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@PedroRocha 

We do not recommend that you use a dedupe policy. This doesn’t mean to say that you can’t, but you’ll likely encounter problems down the line and we would consider this a ‘not supported’ configuration.
 

Why? The reason for this is that, for CS LiveSync, we are mostly backing up sql transaction logs which cannot be deduplicated (anyway) and if a fail over occurs, a deduplication resync will have to occur first, before any further transaction log backups are able to run again.

 

In this case, if there are deduplication database issues, like the DDB not being online for any reason, the transaction logs will not run. This DDB dependency reduces backup resiliency. 


This is the main reason why we recommend non deduplication storage policy to be associated.

If the customer doesn’t want to provision this, then LiveSync may not be a solution for them.

Regards,

Chris

 

Dear Chris,

 

really appreciate your answer, it was very clarifying.

I believe that we should fill a documentation improvement because that requirement is not listed in the planning phase for a livesync scenario.

Here: https://documentation.commvault.com/2022e/expert/102842_planning_for_commserve_livesync_in_windows_environment.html

 

That requirement is shown only on “modifying the default storage policy for livesync”. So if someone doesn’t ever change it, will never know there’s been this requirement. What do you think?

 

Here: https://documentation.commvault.com/2022e/expert/102844_modifying_storage_policy_for_sql_livesync_operations.html


I have a case filled with you guys, is it a definitive answer that this would not be supported down the line or should I ask?

 

regards

Pedro

 

Pedro
Chris Hollis
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@PedroRocha 

I agree, raised one for you >
 


Regarding >

Is it a definitive answer that this would not be supported down the line or should I ask?

Yes, it’s documented for that reason and i don’t see how this could change down the line with the nature of transaction logs, deduplication & the whole purpose of LiveSync, so consider this a definitive answer.

Thanks!

Chris

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@PedroRocha 

In many HSX environment what I do is to create a new storage pool without deduplication and then I create the policy for CS Live Sync pointing to this pool and task completed.

 

Even there is a Media Parameter to allow to create a policy using the library and Media Agent instead of using a storage pool.

 

Of course, you need the Java GUI console for these tasks.

 

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