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Auxiliary copy to tape

  • 23 May 2022
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Good morning to all.

On a monthly basis I release auxiliary copies to tape ending with a total of 11 tapes.

I wanted to do a restore of about 675MB and it asked me for 9 tapes to do it, is this so why the data has been distributed on 9 tapes?

Shouldn't it be on one tape only? Since the size of the L7 tape is large. 

 

Could it be due to the "Use Scalable Resource Allocation" option?
 

Thank you very much for your help.

Best regards,
Johana 😀

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Best answer by Johana 25 May 2022, 14:40

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Userlevel 7
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Hi @Johana 

What setting are you using on the tape copy looking at Multiplexing?

Regarding the "Use Scalable Resource Allocation" option, no I don't believe this is the case.
This option regulates resources, not how a target is being written to.

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Hi @Johana 

What setting are you using on the tape copy looking at Multiplexing?

Regarding the "Use Scalable Resource Allocation" option, no I don't believe this is the case.
This option regulates resources, not how a target is being written to.

 

Hi @Jos Meijer

 

In the Storage Policy: SP_FS_WS_SQL

Primary Copy: Does not have Multiplexing enabled.
Secondary Copy: No Multiplexing enabled

Selective copy (which collects the copies of the secondary copy):

Device Streams of GSCP_COBRA: 1
Multiplexing Factor of GSCP_COBRA: 8

Selective copying (picking up the copies of the secondary):

Device Streams of GSCP_UNIWAY: 1
Multiplexing Factor of GSCP_UNIWAY: 8

Storage Policy Global: GSCP_COBRA

Multiplexing Enabled. 

Multiplexing Factor: 8

Storage Policy Global: GSCP_UNIWAY

Enabled multiplexing. 

Multiplexing Factor: 8


Thanks for your reply.

 

Johana

Userlevel 7
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Depending on how many data is provided for clients in this aux copy, the multiplexing setting can cause data to be spread over multiple tapes. But is not guaranteed to be the cause.

If performance to tape is high enough to keep the tape streaming you can choose to disable multiplexing which will allow data to be placed on the tape without mixing it with other clients.
But you will have to test if this performance meets your requirements.

In order to verify that multiplexing is the cause, if you are using tape storage pools, check if you are not using multiple device streams on the storage pool properties. This will result in spreading client data over multiple tapes.

Badge +4

Depending on how many data is provided for clients in this aux copy, the multiplexing setting can cause data to be spread over multiple tapes. But is not guaranteed to be the cause.

If performance to tape is high enough to keep the tape streaming you can choose to disable multiplexing which will allow data to be placed on the tape without mixing it with other clients.
But you will have to test if this performance meets your requirements.

In order to verify that multiplexing is the cause, if you are using tape storage pools, check if you are not using multiple device streams on the storage pool properties. This will result in spreading client data over multiple tapes.

 

That's right, we are using Storage Pool, but with this configuration: 

Device Streams: 1

Userlevel 7
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That's good, then I would perform tests with mutiplexing disabled.
This should fix your issue regarding data divided over multiple tapes.
But again, only if the performance is sufficient.
If not you can potentially face issues regarding getting data on tape in a timely fashion

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On the other hand, looking at this multiplexing thing that is set to 8, is it set correctly? 

Given that we have 6 storage policies. 
A total of more than 50 clients. 

All their backups are stored on 11 LT07 tapes.

Shouldn't we have 50 configured?

 

Multiplexing Factor: 8 to Multiplexing Factor: 50 aprox.

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Support has told me that it is due to synthetic full backups. 

Multiplexing has nothing to do with it. 

Thank you very much for your answers! 

Userlevel 7
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A synthetic full will be transferred to tape fully rehydrated so blocks will be aligned depending on multiplexing or multi streaming options just like any other backup will.
Something seems to be missing in this definition of the root cause.
Hope you can enlighten us with additional information regarding their findings

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