Full DDB disk - Expand drive or Add DDB-partitions?

Hi, 

We have a situation with filled up DDB drives in a 3-MA grid setup. XL-sized MAs but with 1.3TB DDB NVMe (should be 2TB according to sizing recommendations). 

The reson for the large DDBs seems to be due to a customer backing up a lot of small files that deduplicate quite well, we see between 25-30 billion secondary records and 2.7 billion unique records on the File DDB partitions. 94-95% dedup and performance is exceptional good with this amount of data in the Storage Pool, 60-70µs and ca 660TB. 

We also see pruning working as lowering retention also reduces the secondary records and give us GB back on the DDB volumes. 

We have two options in this hardware…

• We can expand the DDB volumes by concatenating (in Windows) another 1.3TB NVMe to the existing one, giving us 2.6TB on the DDB drives.
• Add one, two or three additional DDB-partitions (one per server) to the DDB, placing them on the extra, available 1.3TB NVMe (MAs in extended mode with 6 DDB partitions, each on a dedicated drive) 

As I see it, the first option will immediately provide more space on the DDB partitions, but is it an optimal setup, with OS-concatenated drives in Windows?

Will the second option help freeing up space on the filled DDB-drives when they already are full or will we still have issues until data is aged off? 

What would be the recommended approach here? 

Regards,

Patrik