When you perform an aux copy of a Dedup job, you actually 'rehydrate' (unravel or explode) the data back to a non-dedup state. As a result.. this causes a lot of very random read IO, and can impact disk read performance in a very big way if you are using SATA as the aux copy source.
You could try to enable multiplexing to increase the the overall throughput, however this may compound the workload issue for the SATA, and make matters worse potentially. Results will be better or worse depending on your storage environment.
SATA disks generally work best when you use them for sequential IO (not random).
Commvault may recommend using SILO backups if that suites, which keeps the data deduplicated all the way to tape (and keeps the SATA read workload sequential).
Auxiliary Copy operations will automatically unravel or explode a deduplicated data. In the case of Auxiliary Copy, if the secondary copy is set up for Deduplication, then the deduplication store gets created for the copy and the associated data is deduplicated for secondary copy. The Auxiliary copy follows the deduplication type (both block level and object level) of the Source Copy.
- Data in a storage policy copy enabled for Deduplication can not be multiplexed. Therefore, Data Multiplexing is not supported if the storage policy copy is enabled with Deduplication. However, a SILO copy supports Data Multiplexing even if the storage policy copy is enabled with Deduplication.
- Multiplexed data cannot be copied to a storage policy copy enabled for Deduplication. Therefore, a storage policy copy enabled for Deduplication can not have a direct or indirect source copy enabled for Data Multiplexing.
- An Auxiliary Copy can be configured with Data Multiplexing when the source copy is enabled for Deduplication.