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MSSQL Backup Issue

  • 4 November 2021
  • 6 replies
  • 57 views

Userlevel 2
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Hi Fellas,

 

How should I interpret it according to the screenshot below, do you think Job is wasting time in DDB lookup?

 

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Best answer by Mike Struening 4 November 2021, 16:03

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Userlevel 7
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Hi @0ber0n 

I would definitely interpret those figures that a large proportion of that time is spent with DDB look ups.

However, there might be many reasons why that task is taking time and we would need more background info to understand.

DDB responsiveness can be caused by many different factors, to give an idea:

  • What is the average Q&I time for the DDB - is the DDB performance poor all round?
  • What is the relative distance and connectivity between the client and the DDB MA?
  • What other tasks/jobs is the DDB MA performing during these jobs?
    • Are DDB backups happening during these times that will increase response times
    • Are these jobs happening during a pruning window when the DDB is busy checking for records to be pruned
  • Is the DDB hosted on fast storage?
  • Is the DDB MA up to spec for the environment size or workloads assigned?

 

These are a few things to consider, let me know if these questions help identify any potential issues.

Thanks,

Stuart

Userlevel 2
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Hi Stuart,

 

Acctually, I really have strong MA, Local SSD for the DDB and Index Cache and also 40gb nw connection between MA and client.

I suspect to the DDB Store. As you can see there are 3 SIDB and the backups are writing to the SIDB: 78 which has poor Q%I time.

The questions here:

1- Commvault created the new SIDB but why the backups are not moved automatically to the new SIDB ?

2- I manually moved my backups with the workflow(Move Clients To New DDB) from SIDB:78 to SIDB: 86. But why it is not moved to the SIDB:94

Userlevel 7
Badge +14

Hi @0ber0n 

Those SIDB IDs aren’t clear from the screenshot provided, I can only see the job history and 2 highlighted job details.

We would need more info to make any assertions on DDB behaviour.

If your MA spec and DDB configuration is good, then we would need to look and understand why Q&I times are poor, then additionally why moving clients to a new DDB hasn’t worked as expected.

Thanks,

Stuart

Userlevel 2
Badge +6

sorry I forget to the add screenshot. here is it:

 

 

Userlevel 7
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@0ber0n , I see you have 2 partitions on these….curious if at any time the partitions were offline?  If blocks that were on A now had to write to B, that would cause some issues as well.

Overall, you have a large store (focusing on 78 which is our main offender) which is rather old (not that age alone is a factor).

Dedupe performance is almost always down to the disks thermselves, otherwise it’s scale.

Have you run iometer to eliminate the disks as an option?

https://documentation.commvault.com/11.24/expert/8825_testing_iops_of_deduplication_database_disk_on_windows_01.html

Definitely worth considering.

Also worth checking out the dedupe hardware reqs:

https://documentation.commvault.com/11.24/expert/111985_hardware_specifications_for_deduplication_mode.html

Based on what I see, you are set for Extra Large with 2 DDB disks, so that’s where I’d start looking (though you know your environment better).

Now if EVERYTHING checks out, iometer and all, might be worth a case though my impression at this point is either the hardware is not up to the task, or you’re edging up to the limits and need to seal.

Userlevel 7
Badge +14

@0ber0n 

As @Mike Struening suggests, ruling out any potential hardware bottleneck or sizing guideline being the first task.

The only differentiating factor I can see between the 2 new DDBs is Application Size, I would need to check with the teams here on the principles actioned by the Move Clients To New DDB workflow.

The only idea I have right now is that it may selects a new destination DDB for a client based on Application Size already covered by the potential target DDBs with 86 lower than 94, so more open to new clients.

Thanks,

Stuart

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