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Question

DDB location path - best practices

  • August 12, 2025
  • 2 replies
  • 81 views
J
Novice
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Hi,

according to BOL Deduplication Building Block Guide,

  • a Media Agent can host up to two (2) DDBs (from on LUNs of different RaidGroup)
  • ALL DDBs of all Storage Pools on a Media Agent should share the same volume / paths (e.g. D:\DDB)

My question is now, does this require to create a streched / expanded Volume accross multiple (2) LUNs / Disks ?
otherwise I don’t get, how one single directory or volume can be used to place the data to mutiple LUNs

and should this be a striped or a concatinated volume layout ?
In the past I used D:\DDB and E:\DDB as paths (different volumes on different LUNs).
This doesn’t seem to be best practice anymore, if I understand the BOL entry correct.

I could understand, if this restriction is valid for all (3 horizontal scaling) DDBs belonging to the same Pool. But the article states, that all pools should use the same volume or path.

rgds
Klaus

2 replies

Emils
Vaulter
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  • EmilsVaulter
  • Vaulter
  • August 15, 2025

Hi ​@johanningk 

Thanks for reaching out. 

I’m assuming you're referring to the following points in the documentation:

  • Configure LUNs so that no more than one DDB is configured on any one RAID group.

  • Configure only two DDBs per MediaAgent with two different LUN groups.

  • You must use only one deduplication database (DDB) path for all the storage pools that are associated with a MediaAgent. The DDB path can be root directory of a drive (for example, D:) or a folder (for example, D:\DDB) on the MediaAgent.

 

If so, let's focus on the LUNS component: 

So a single MediaAgent is to be configured with a max of 2x different DDB engines.

For each DDB engine, associate a single a LUN from a unique RAID group.

Each DDB engine, associate it to a single path eg. D:\DDB, please note a DDB engine can be associated to multiple storage pools ( eg. global Dedupe). 

Also each engine can have multiple partitions within the same MediaAgent, they need to exist within the same location D:\DDB. It is not recommended to move a partition to another location eg. f:\DDB for the same engine.

Now for the second DDB Engine, you can create another LUN ( from another RAID GROUP) and assign E:\  and create the DDB within this location, eg. E:\DDB for engine 2 within the same MediaAgent. 

Hope this clears a bit better.

J
Novice
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  • johanningkNovice
  • Author
  • Novice
  • August 15, 2025

Thanks Emils,

in  that case the phrases used in BOL to explain this setting are misleading or at least not precise.

The other thing is, that I understand that each storage Pool is a unique combination of DDB Engine and Disk/Cloud - library path and has its own DDB (paths). Only if you create derived plans or storage policies, you can associate them to an existing Pool. (global dedupe; shared/common library paths)

But maybe I simply associate different meanings to the words used in BOL, as {you do|Commvault does}.

Since the wording seem to be changed every 2-4 SP/FR/PR of Commvault software, sometimes its hard to catch up  😉

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